as101-everything-together

7. Imagine you are waiting on a train platform while a train passes by at 100 km/h. If it is blowing its whistle during this time, what will you observe about the pitch (frequency) of the whistle? (a) As the train approaches it will be higher than usual and as it leaves it will be lower. (b) As the train approaches it will be lower than usual and as it leaves it will be higher. (c) The pitch will sound the same the whole time. (d) The pitch will be higher the whole time. 8. What must be true about a star that we observe to be 8 light years away? (a) It must be very large relative to the Sun. (b) We are seeing the star as it was 8 years ago since the light would have taken that long to reach us. (c) The star formed about 8 million years ago. (d) The light we observe has taken so long to reach us that the star probably no longer exists. 9. About how long does it take light to cross our galaxy? (a) 80,000 years (b) 8 minutes (c) Light travels in_nitely fast so no time at all. (d) 4.5 billion years 10. Which sequence correctly orders objects from smallest to largest? (a) Earth, solar system, Milky Way galaxy, the Universe (b) Earth, Milky Way galaxy, solar system, the Universe (c) Earth, solar system, the Universe, Milky Way galaxy (d) solar system, Earth, Milky Way galaxy, the Universe 11. Which one of the following statements regarding stars and constellations is true? (a) Only stars near the ecliptic belong to constellations. (b) Every star now belongs to a constellation. (c) Constellations include only stars visible to the naked eye. (d) There are several constellations containing no stars at all. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

*b. the light lef the star 2.538×10 6 years ago c. orbitng a diferent Solar System d. located in the centre of the local supercluster Q:5 If the life of a star is 5, 000,000,000 years and its distance from the Earth is 1,000, 000 ly is there any chance that the star might be dead by now mean while its light is stll traveling towards the Earth? a. Yes *b. No c. Maybe Q.6 What is the average distance of the Earth to the a (alpha) Centauri star ? a. 4.37 ly *b. 5.2 ly c. 4.0 ly d 6.8 ly Q.7 The following circle to represent the star Antares’ or a (alpha) Bootes diameter d Antares and the scale given by the line segment = =100 R SUN ( equal to 100 tmes the radius of the sun). How big is approximately Antares in relaton to the sun? a. 20 tmes c. 16 tmes *b. 7 tmes d. 30 tmes Q.8 Which of the following is the smallest? a. The size of a galaxy b. The radius of the solar system *c. The planet Jupiter diameter d. The diameter of Antares Q.9 It takes light 1.3 seconds to travel from the Moon to Earth and 8 minutes for light to travel from the Sun to Earth. Which of the following statements is true? a. The Sun is 6.2 tmes farther from Earth than the Moon b. The Sun is 10 tmes farther from Earth than the Moon. *c. The Sun is 370 tmes farther from Earth than the Moon d. The Sun is 1800 tmes farther from Earth than the Moon Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Q.21 At which positon (A, B, C) is the gravitatonal force of the Earth on the spaceship going to the Moon is the greatest? MOON EARTH A B C a. A b. B c. *C Q. 22 Two metal spheres each have mass of 3.0 x 10 8 kg. If the gravitatonal force of atracton between them is 37.5 N, what is the distance between their centers of mass? *a. 400.1 m b. 150 m c. 399.5 m d. 500 m Q.23 X-rays easily penetrate the Earth’s atmosphere and reach the ground from space a. True *b. False Q. 24 .What is the ratio of the light-gathering power of a future 40-metre telescope to that of a 1-metre telescope a. 40 to 1 b. 1 to 40 *c. 1600 to 1 d. 1 to 1600 Q. 25 What happens to a telescope’s light-gathering power and resolving power when you increase its diameter? a. Its light-gathering power increases and its resolving power decreases b. Its light-gathering power decreases and its resolving power decreases *c. Its light-gathering power and resolving power both increase Q. 26 Which object is located at one foci of the elliptcal orbit of Mars? *a. The sun b. Earth Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

a) Venus, Saturn, Moon, Andromeda galaxy, Polaris b) *Moon, Venus, Saturn, Polaris, Andromeda galaxy *b) c) Polaris, Andromeda galaxy, Moon, Saturn, Venus d) Andromeda galaxy, Saturn, Venus, Polaris, Moon. OR a) Alpha Centauri, Uranus, Mercury, Small Magellanic Cloud, Coma Supercluster b) Mercury, Uranus Alpha Centauri ,Small Magellanic Cloud, Coma Supercluster , *b) c) Cloud, Coma Supercluster, Mercury, Small Magellanic Cloud, Uranus d) Small Magellanic Cloud, Coma Supercluster, Alpha Centauri, Uranus, Mercury Q:4 The nearest star to our solar system is alpha Centauri at 4.0  10 16 m (4.3 ly away). The diameter of the sun is 1.4  10 9 m. How many suns would it take to line up adjacent to each other in order to reach alpha Centauri? a) 5.6  10 6 , b) 5.6  10 6 , c) 2.8  10 25 *d) 2.8  10 7 Q:5 There approximately 100 billion stars in our galaxy. If there 100 billion observable galaxies in our universe, what is a reasonable estmate for the total number ion the universe? *a) 1.0  10 22 b) 2.0  10 20 c) 1.5  10 15 d) 1.0  10 24 Q:6 The distance to a super cluster galaxy might be: *a) 100 Mpc b) 10 Kpc c) 120 Ly d) 10 AU Q:7 Approximately 100 Earths would ft inside Jupiter. This Jupiter’s radius must be …………….tmes larger that Earth’s radius. a) 100 b) 12 *c)10 d) 1000 Q:8) A spherical partcle in the ring of Saturn has radius of about 1m. The surface area of the partcle in the area of radiaton fow is: a) 125 m 2 b) 3.14 m 2 *c) 12.6 m 2 d) 14 m 2 Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Q: 1 Which of the following definitions best describes a constellation? *a. a region of the sky containing a certain star pattern b. a group of very bright stars c. a group of very faint stars d. the dividing line between the north and south celestial hemispheres Q:2 Which of the following best describes the Big Dipper? *a. an asterism b. a faint star near Polaris c. the North Star d. a constellation Q:3 . What do stars in the same constellation have in common? a. They probably formed at the same time. b. They must be part of the same cluster of stars in space. c. They must have been discovered at about the same time. *d. They are in the same part of the sky as seen from the Earth. Q: 4 What languages do the standard constellation names come from? *a. Greek and Latin b. Latin and Arabic c. Greek and Arabic d. Arabic and Sanskrit Q:5 Table 2-1 Star Name Apparent Visual Magnitude δ Dra 3.07 α Cet 2.53 Nim 8.07 α CMa −1.46 Refer to Table 2-1. Which star in the table would appear brightest to an observer on Earth? a. δ Dra b. α Cet c. Nim *d. α CMa Q:6 What causes the precession of the Earth’s rotation axis? *a. the force of gravity from the Sun and Moon on the Earth's equatorial bulge b. the force of gravity from the Sun and Jupiter on the Earth–Moon system c. the magnetic field of the Earth Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Q:15 The star Vega has an apparent visual magnitude of 0.03 and the star HR 4374 has an apparent visual magnitude of 4.87. It has been determined that both stars are at the same distance from the Earth. What does this information tell us about the two stars? a. Together the two stars would have a magnitude of 4.9. b. Vega must produce less energy per second than HR 4374. *c. Vega must produce more energy per second than HR 4374. d. Vega will appear fainter to us than HR 4374. Q:16 . What is the apparent visual magnitude of a star a measure of? a. the star’s size as perceived by human eyes on Earth b. the star’s temperature as perceived by human eyes on Earth c. the star’s colour as seen by human eyes on Earth *d. the star’s brightness as seen by human eyes on Earth Q: 17 Which of the following is equivalent to one-3,600 th of a degree? a. precession *b. second of arc c. minute of arc d. angular diameter Q: 18 What is the term for the point on the celestial sphere directly above an observer, no matter where on the Earth the observer is located? a. north celestial pole b. south celestial pole *c. zenith d. nadir Q: 19 Where is the zenith for an observer standing at a point on the Earth’s equator? *a. directly overhead b. near the horizon and towards the south c. near the horizon and towards the west d. the position depends on the time of day Q: 20 If the Earth had an orbital tlt of 0 degrees ( obliquity) then: a. The direct rays of the sun would shine on the equator b. Day and night would be 12 long every day everywhere on the Earth c. An observer at the equator would see the sun pass at zenith every day d. There would not be no seasons *e. All of the above Q: 21 The orbit of the Earth had an eccentricity 0.017. If the eccentricity increased to 0.65 what would happened to the Earth’s sesons? e= 0.017 e = 0.65 Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

*a. 50° N b. 50° S c. 90° N d. 90° S Q. 35 An observer in the northern hemisphere takes a time exposure photograph of the night sky. If the illustration depicts the photograph taken by the observer, which direction was the camera pointing? *a. due north b. due south c. due west d. straight up, directly overhead Q.36 An observer in the northern hemisphere takes a time exposure photograph of the night sky. If the illustration depicts the photograph taken by the observer, which direction was the camera pointing? a. due north *b. due south c. due east d. straight up, directly overhead Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Q.37 An observer in the southern hemisphere takes a time exposure photograph of the night sky. If the illustration depicts the photograph taken by the observer, which direction was the camera pointing? a. due north b. due south *c. due east d. due west Q: 38 Where in the sky would an observer at the Earth's equator see the celestial equator? a. The celestial equator would be at 45 degrees above the northern horizon. b. The celestial equator would be at 45 degrees above the southern horizon. c. The celestial equator would coincide with the horizon. *d. The celestial equator would be directly overhead. Q:39 Which of the following best defines the ecliptic? a. the plane that is perpendicular to the Earth's axis of rotation b. the projection of the Earth's equator onto the sky c. the path traced out by the Moon in our sky in one month against the background stars *d. the path traced out by the Sun in our sky over one year against the background stars Q: 40 Which of the following best defines the ecliptic? a. the plane that is perpendicular to the Earth's axis of rotation b. the projection of the Earth's equator onto the sky c. the path traced out by the Moon in our sky in one month against the background stars *d. the path traced out by the Sun in our sky over one year against the background stars Q:41 Which of the following describes a concept very similar to latitude? a. right ascension *b. declination c. magnitude d. meridian Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

1. In 1054 CE, the Chinese recorded a very interesting and powerful cosmic event. What was this event? a. a star merger * b. a supernova c. a galactic collapse d. simultaneous solar and lunar eclipses 2. What was a common feature of astronomy as practiced worldwide prior to the Greeks? * a. recognizing patterns b. making hypotheses c. defining the 24-hour clock d. observing supernovae 3. What did Eratosthenes measure very accurately? * a. the size of the Earth b. the length of the year c. the distance to the Moon d. the length of the month 4. Who were the two great authorities of Greek astronomy? * a. Aristotle and Ptolemy b. Julius Caesar and Aristotle c. Columbus and Ptolemy d. Alexander the Great and Julius Caesar 5. Whose writings became so famous that he was known throughout the Middle East simply as “The Philosopher”? a. Ptolemy b. Eratosthenes * c. Aristotle d. Hipparchus 6. Which of the following statements reflects beliefs that were almost universally held in pre- Copernican astronomy? a. The planets travelled in elliptical orbits around the Earth. b. The planets travelled in elliptical orbits around the Sun. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

c. The Sun was at the centre of the universe. * d. The Earth was at the centre of the universe. 7. In what circumstances is retrograde motion observable? a. It is observable for planets located between the Earth and the Sun. * b. It is observable for planets more distant from the Sun than the Earth c. It is only observable for the Moon. d. It is observable for all planets. 8. You are observing the night sky from Mars. In what circumstances is retrograde motion observable? * a. It is observable for planets more distant from the Sun than Mars. b. It is observable for planets located between Mars and the Sun. c. It is only observable for Earth and Venus. d. It is observable for all planets. 9. What is the term for the apparent westward motion of a planet in the sky compared to the background stars (as viewed from the Earth) when observed on successive nights? a. epicycle * b. retrograde motion c. prograde motion d. heliocentric motion 10. What is parallax? * a. the apparent motion of an object due to the motion of the observer b. the distance between two straight lines c. the small circle that the planets slid along in Ptolemy’s geocentric universe d. the distance between two foci of an ellipse 11. What was the reason for using epicycles and deferents to explain the motion of the planets in the night sky? a. prograde motion b. Mercury and Venus’s limited angular distance from the Sun * c. retrograde motion d. non-uniform speed of the planets in their orbits 12. Why did ancient astronomers believe that the Earth did not move? * a. because they could not detect parallax b. because they believed in circular motion Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

c. because all observable planets follow retrograde motion d. because parallax is only detectable during the day 13. In Ptolemy’s view of the universe, what is at the centre of a planet’s epicycle? a. the Sun b. the Earth * c. the deferent d. the equant 14. What is the term for a small circle that has its centre located on the circumference of another larger circle? a. equant b. deferent c. retrograde loop * d. epicycle 15. What feature of Ptolemy’s model of the universe made it possible to explain retrograde motion? a. heliocentrism b. elliptical orbits * c. epicycles d. geocentrism 16. Which of the following astronomers described the universe in a way that matches the diagram? a. Kepler * b. Ptolemy c. Copernicus d. Galileo Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

17. The Copernican system was no more accurate than the Ptolemaic system in predicting the positions of the planets because of a key factor that was unchanged from the Ptolemaic system. What was that factor? a. The Copernican system assumed the Earth was at rest at the centre. b. The Copernican system used elliptical planetary orbits. * c. The Copernican system used uniform circular motion. d. The Copernican system assumed all planets orbited the Sun. 18. What is the book “De Revolutionibus Orbium Coelestium” about? a. It describes how Galileo’s observations and Kepler’s calculations proved the Copernican theory. b. It describes the construction of Galileo’s telescope and his observations. c. It is a dialogue written to convince the general public of the merits of the Copernican theory. * d. It lays out the Copernican theory for the first time. 19. What was the greatest inaccuracy in Copernicus’s model of the solar system? * a. that the planets travelled in circular orbits with uniform motion b. that the planets travelled on epicycles, the centres of which followed orbits around the Sun c. that the planets travelled in elliptical orbits d. that the planets were allowed to travel backwards in their orbits 20. Which of the following objects cannot transit (i.e. pass in front of) the Sun, as seen from Jupiter? * Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

1. Why do astronomers build radio telescopes? *a. Radio waves give a different view of the universe. b. Radio waves from space reach the Earth’s surface. c. Radio telescopes can detect signals from aliens. d. Radio telescopes can be much larger than optical telescopes. 2. What type of telescope is most likely to suffer from chromatic aberration and have a low light- a. a small diameter reflecting telescope b. a large diameter reflecting telescope *c. a small diameter refracting telescope d. a large diameter refracting telescope 3. When does chromatic aberration occur in a telescope? a. when different colours of light do not focus at the same point in a reflecting telescope *b. when different colours of light do not focus at the same point in a refracting telescope c. when light of different wavelengths gets absorbed by the mirror in a reflecting telescope d. when light of different wavelengths gets absorbed by the lens in a refracting telescope 4. What type of telescope is a radio telescope? *a. reflecting b. refracting c. deflecting d. retracting 5. What type of telescope has a lens as its objective and contains no mirrors? a. deflecting b. reflecting Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

*c. refracting d. compound 6. How is the objective of most radio telescopes similar to the objective of a reflecting optical tel *a. They are both bowl-shaped (concave). b. They are both hill-shaped (convex). c. They are typically the same size. d. They are both made of metal. 7. What type of primary is found in a reflecting telescope? a. prism *b. mirror c. lens d. diffraction grating 8. You point your backyard reflecting telescope at the star Vega. Where does Vega’s light go? *a. from the primary mirror, to the secondary mirror, to the eyepiece b. from the primary mirror to the eyepiece c. through the primary lens, to the secondary mirror, to the eyepiece d. through the primary lens, through the secondary lens, to the eyepiece 9. Which of the following best explains the concept of atmospheric windows? a. Holes in the Earth’s atmosphere allow ultraviolet radiation to reach the North and South p b. X-ray radiation from space can see through the atmosphere to observe activities on the gro *c. Only certain wavelengths of electromagnetic radiation from space reach the Earth’s surfac d. The Earth’s atmosphere can be “closed” or “open” to electromagnetic radiation, dependin 10. What is the main reason for building large optical telescopes? Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

a. It’s the best way to see through clouds and other light-absorbers in the atmosphere. *b. It’s the best way to collect as much light as possible from faint objects. c. It’s the best way to nullify the blurring effects of the Earth’s atmosphere and thus produce d. It’s the best way to magnify objects and make them brighter. 11. An astronomer takes two pictures of the same object using the Hubble Space Telescope. One *a. Blue light will show finer details. b. Red light will show finer details. c. Both should be the same. d. The amount of detail depends on the distance to the object. 12. Which property of a telescope determines its light-gathering power? a. the focal length of the objective b. the focal length of the eyepiece *c. the diameter of the objective d. the length of the telescope tube 13. What is the light-gathering power of a telescope directly proportional to? *a. the diameter of the primary mirror or lens b. the focal length of the primary mirror or lens c. the length of the telescope tube d. the diameter of the eyepiece 14. Why can’t a telescope image be magnified to show any level of detail? *a. Diffraction limits the amount of detail that is visible. b. Telescopes only view a small region of the sky. c. Magnification depends on focal length. d. Resolving power depends on wavelength. 15. Which of the following has the most light-gathering power? a. a telescope of 5 centimetres diameter and focal length of 50 centimetres Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

*b. a telescope of 6 centimetres diameter and focal length of 100 centimetres c. a telescope of 2 centimetres diameter and focal length of 100 centimetres d. a telescope of 3 centimetres diameter and focal length of 75 centimetres 16. How is the resolving power of a telescope defined? *a. It is a measure of the minimum angular separation that can be seen with the telescope. b. It is a measure of the amount of light that the telescope can gather in one second. c. It is the separation between the objective and the image. d. It is a measure of how blurry objects appear in the telescope. 17. What happens to a telescope’s light-gathering power and resolving power when you increase *a. Its light-gathering power and resolving power both increase. b. Its light-gathering power increases and its resolving power decreases. c. Its light-gathering power decreases and its resolving power increases. d. Its light-gathering power and resolving power both decrease. 18. What can be done to improve the resolving power of ground-based optical telescopes? a. Use them at longer wavelengths. *b. Equip them with an adaptive optics system. c. Change them from reflectors to refractors. d. Increase their focal length. 19. The pupil of the human eye is approximately 0.8 centimetres in diameter when adapted to the a. 2 : 1 b. 20 : 1 c. 400 : 1 Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

*d. 40,000 : 1 20. What is the ratio of the light-gathering power of a 10-metre telescope to that of a 1-metre telescope? a. 10 to 1 b. 1 to 10 *c. 100 to 1 d. 1 to 100 21. The diagram below illustrates the layout and light path of a reflecting telescope of the ____________________ design. ANSWER: Cassegrain 22. A(n) ____________________ is used to measure the brightness and colour of stars. *ANSWER: photometer 23. 300 nanometre light has a lower frequency than 500 nanometre light. a. True *b. False 24. X-rays easily penetrate the Earth’s atmosphere and reach the ground from space. a. True *b. False Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

25. What is the purpose of interferometry? *a. It is used to improve the resolving power of telescopes. b. It is used to decrease the chromatic aberration of a telescope. c. It is used to make large X-ray and ultraviolet telescopes. d. It allows radio telescopes to be within a few hundred feet of each other. 1. Which of the following statements best describes the wavelength of a wave? a. the measure of how strong the wave is *b. the distance between two adjacent peaks of the wave c. the measure of how fast the wave is d. the distance between a peak of the wave and the next trough 2. Which form of electromagnetic radiation travels fastest? a. gamma rays b. radio waves *c. all electromagnetic radiation travels at the same speed d. the speed of radiation depends on the brightness of the source 3. What does the word “radiation” mean when used by scientists? a. invisible forms of light such as X-rays and radio waves b. the light emitted by black holes and protostars c. high-energy particles from nuclear reactors *d. anything that spreads out from a central source 4. What does a nanometre measure? a. frequency b. energy c. mass *d. length Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

5. In which way is a photon of blue light identical to a photon of red light? a. energy *b. speed c. wavelength d. frequency 6. Which of the following types of light has wavelengths that are longer than the wavelengths of visible light? a. gamma rays b. ultraviolet *c. infrared d. X-rays 7. What is the longest wavelength of light that can be seen with the human eye? a. 400 nanometres *b. 700 nanometres c. 7000 nanometres d. 3×10 8 m 8. How does long-wavelength visible light appear to the average human eye? a. invisible b. green c. blue *d. red 9. What is the relationship between colour and wavelength for light? *a. Wavelength increases from blue light to red light. b. Wavelength decreases from blue light to red light. c. All colours of light have the same wavelength. d. Wavelength depends on intensity, not colour. 10. Which of the following sequences of electromagnetic radiation shows the order of increasing energy correctly a. gamma rays, X-rays, infrared, radio *b. visible, ultraviolet, X-rays, gamma rays Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

c. visible, microwave, radio, infrared d. infrared, visible, radio, X-rays 11. Which of the following types of light has wavelengths that are shorter than the wavelengths of visible light? *a. gamma rays b. radio waves c. infrared radiation d. microwaves 12. Which of the following types of electromagnetic radiation has the smallest frequency? a. X-rays *b. radio waves c. visible light d. infrared radiation 13. Which of the following types of electromagnetic radiation has the greatest energy per photon? a. X-rays b. radio waves *c. gamma rays d. infrared radiation 14. Which of the following types of electromagnetic radiation has the lowest energy per photon? a. X-rays b. ultraviolet light c. gamma rays *d. infrared radiation 15. Which of the following statements about the Earth’s atmosphere is true? *a. The atmosphere is transparent to most radio waves. b. The atmosphere is opaque to most radio waves. c. The atmosphere is transparent to X-rays. d. The atmosphere is opaque to most visible wavelengths. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

16. How does the energy of a photon relate to the other properties of light? a. Energy is directly proportional to the wavelength of the light. *b. Energy is inversely proportional to the wavelength of the light. c. Energy depends only on the speed of the light. d. Energy is inversely proportional to the frequency of the light. 17. How do photons of blue light differ from photons of red light? *a. Blue light photons have more energy than photons of red light. b. Blue light photons have a lower frequency than photons of red light. c. Blue light photons have a longer wavelength than photons of red light. d. Blue light photons travel faster than photons of red light. 18. What statement below best describes the refraction of light? a. the absorption of light as it travels though a dense, transparent material b. the spreading out of white light according to wavelength *c. the change in direction of a light ray as it passes to a medium of different optical density d. the change in direction of a ray of light as it reflects off a surface 19. What is a photon? a. a type of electromagnetic radiation b. a particle within the atmospheric window c. a particle produced when light interacts with vacuum *d. a particle of light 20. Which of the following types of electromagnetic radiation is absorbed by water lower in the Earth’s atmosphe *a. infrared radiation b. ultraviolet radiation c. radio wave radiation d. X-ray radiation 21. Which of the following types of electromagnetic radiation is absorbed by ozone in the Earth’s atmosphere? a. infrared radiation *b. ultraviolet radiation c. X-ray radiation Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

d. visible light 22. What is a similarity between radio and optical telescopes? *a. Both can observe from the Earth’s surface. b. Both are usually located on mountaintops. c. Both are usually made as refracting telescopes. d. Both can detect radiation with charge-coupled devices. 1. How can the density of the Sun be measured? a. by using the density of hydrogen as measured on Earth b. by analyzing samples of the solar wind c. by using the amount of area covered by Venus during a transit d. *by using Newton’s laws and the Sun’s diameter 2. What is the defniton of Absolute Zero? a. zero degrees Celsius *b. the temperature at which no thermal energy can be extracted from atoms c. the temperature at which water freezes d. the temperature at which molecules split into atoms 3. The temperature of an object is 273K. What is the temperature in degrees a. 273 b.-273 *c. 0 d. 373 4. The temperature of an object is 373K. What is the temperature in degrees Celsius? a. -273 * b.-173 c. 173 d. 273 5. What is the temperature of an object from which no heat energy can be extracted? *a. 0 Kelvin b. 100 Kelvin Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

c. 100 Celsius d. Celsius 6. The surface temperature of the Sun is about 5800K. Based on this temperature, what is the expe a. orange * b. green c. yellow d. red 7. Which of the following measures the average speed of the partcles (atoms or molecules) in a gas? a. Heat b. Compositon *c. Temperature d. Binding energy 8 . A plot of the contnuous spectra of four diferent stars is shown in the fgure. Based on these spectra *a. A b. B c. C d. D . 9. A plot of the contnuous spectra of four diferent stars is shown in the fgure. Based on these spectra, which o a. A b. B c. C *d. D Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

10. The Sun emits its maximum intensity of light at about 520 nm. According to Wien’s Law, at what wavelength *a. 260 nm b. 1040 nm c. 5800 nm d. 11600 nm 11 . What is the sequence of star colours in order of increasing temperature? *a. red, yellow, blue b. red, blue, yellow c. yellow, blue, red d. blue, yellow, red 12. Is it possible for a red star to emit more energy than a blue star? a. No, because the red star has a lower temperature. * b. Yes, if the red star has a larger area. c. Yes, if the red star has a larger wavelength of maximum intensity. d. No, because red stars are less massive than blue stars. 13. The Stefan-Boltzmann law says that hot objects emit energy proportonal to the fourth power of their tempe more energy per second will the hoter star radiate from each square meter of its surface? (Please see appendix a. 5 tmes b. 25 tmes *c. 625 tmes d. 10 15 tmes 14. What is the explanaton for the patern of granulaton seen on the visible surface of the Sun? a. The granules form the base of a circulaton patern that extends from the photosphere to the outer corona. b. The granules are regions of nuclear energy generaton in the photosphere of the sun c. Each granule contains a strong magnetc feld, which compresses and heats the gas underneath it. * d. The granules are the tops of hot gases that have risen from the Sun's convectve Zone 15. What is found in the centers of granules? *a. hot material rising to the photosphere from below b. cool material falling from the photosphere to the regions below c. material that is fainter and hoter than its surroundings d. material that is brighter and cooler than its surroundings Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

16. What is responsible for binding the electrons to the nucleus? a. Kirchhof's law b. Wien’s law *c. Coulombs Law d. Balmer series 17. Which of the following is a set of rules that describes how atoms and subatomic partcles behave? a. Kirchhof's law b. Wien’s law *c. Quantum Mechanics d. General Relatvity 18. What is the lowest energy level in an atom called? *a. Ground State b. The absolute zero temperature c. The ionizaton level d. The energy level from which the Paschen series of hydrogen originates 19. The energy of the frst level in an atom is 2.2 × 10 -18 J, and the energy of the second energy level is 1.6 a. 3.5 × 10 -36 J * b. 6.0 × 10 -19 J c. 3.5 × 10 -18 J d. 6.0 × 10 -18 J 20. The diagram illustrates a light source, a gas cloud, and three diferent lines of sight (the observer is locat a. 1 Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

b. 2 *c. 3 21. Which of the following can be determined from the spectrum of a star, without additonal informaton? *a. radial velocity b core temperature c. distance d. velocity across the sky 22. Which of the following is a property of the Sun’s chromosphere? a. produces a coronal fltergram b. is below the visible surface of the Sun c. is above the corona * d. hoter than the photosphere 23 . BONUS queston : A boy has mass equal to 35 kg on the surface of the Earth? What is his weight on the surfa *a. 9579.5 N b. 343.35 N c. 957.95 N d. 3.43 N 2. How can the density of the Sun be measured? a. by using the density of hydrogen as measured on Earth b. by analysing samples of the solar wind c. by using the amount of area covered by Venus during a transit d. *by using Newton’s laws and the Sun’s diameter 3. Which two quanttes are needed to calculate density of any object? a. *mass and volume b. temperature and diameter c. mass and temperature d. volume and temperature 3. What is the defniton of Absolute Zero? a. zero degrees Celsius *b. the temperature at which no thermal energy can be extracted from atoms c. the temperature at which water freezes d. the temperature at which molecules split into atoms 4. The temperature of an object is 273K. What is the temperature in degrees Celsius? a. 273 Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

b.-273 *c. 0 d. 373 5. The temperature of an object is 373K. What is the temperature in degrees Celsius? a. -273 * b.-173 c. 173 d. 273 6. What makes up the neutral hydrogen atom? a. one proton one neutron b. one proton c. one proton one neutron one electron *d. one proton one electron 7. What is the temperature of an object from which no heat energy can be extracted? *a. 0 Kelvin b. 100 Kelvin c. 100 Celsius d. Celsius 8. Summer temperatures on Mars can reach 310 K. How would humans deal with such a temperature o a. This temperature is so low that a human would freeze to death b. This is a Canadian winter temperature; humans could survive with a winter jacket and boots * c. This is a Canadian summer temperature; humans could be comfortable in shorts and a T-shirt d. This temperature is so high that a human would die of heatstroke 9. Which of the following contains two or more atoms that are bound together by exchanging or sharing a. nucleus b. ion c. proton *d. molecule 10. The surface temperature of the Sun is about 5800K. Based on this temperature, what is the expected a. orange * b. green c. yellow d. red 11. What does a non-ionized atom always contain? a. the same number of protons and neutrons * b. the same number of protons and electrons Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

c. twice as many protons as neutrons d. twice as many neutrons as protons 12. Which of the following measures the average speed of the partcles (atoms or molecules) in a gas? a. Heat b. Compositon *c. Temperature d. Binding energy 13 . A plot of the contnuous spectra of four diferent stars is shown in the fgure. Based on these *a. A b. B c. C d. D . 14. A plot of the contnuous spectra of four diferent stars is shown in the fgure. Based on these spectra, which a. A b. B c. C *d. D 15. The Sun emits its maximum intensity of light at about 520 nm. According to Wien’s Law, at what wavelength *a. 260 nm b. 1040 nm c. 5800 nm d. 11600 nm 16. The Sun emits its maximum intensity of light at about 520 nm. According to Wien’s Law, what would the tem *a. 1040 K b. 2900 K c. 5800 K d. 10400 K Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

17 . What is the sequence of star colours in order of increasing temperature? *a. red, yellow, blue b. red, blue, yellow c. yellow, blue, red d. blue, yellow, red 18. Is it possible for a red star to emit more energy than a blue star? a. No, because the red star has a lower temperature. * b. Yes, if the red star has a larger area. c. Yes, if the red star has a larger wavelength of maximum intensity. d. No, because red stars are less massive than blue stars. 19. Where does most of the visible light we see coming from the Sun originate? a. Chromosphere * b. Photosphere c. Corona d. Sunspots 20. What is the phase of mater in the Sun? a. Solid * b. Plasma c. Gas d. Liquid 1. What is the spectral sequence in order of increasing temperature? a. MKFAGBO b. BAFGKMO *c. MKGFABO d. ABFMKGO 2. Which of the following can we use to determine the surface temperature of a star? a. determining if the star has a companion star *b. studying its line absorption spectrum c. measuring the star’s distance d. measuring the star’s parallax Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Table 1 Star Name Spectral Type α For F8 ο Cet M7 γ Tri A0 ξ Per O7 3. The table lists the spectral types for each of four stars. Which star in this table would have the lowest surface te a. α For *b. ο Cet c. γ Tri d. ξ Per 4. The table lists the spectral types for each of four stars. Which star in this table would have the highest surface t a. α For b. ο Cet c. γ Tri d. ξ Per ANSWER: d 5. What properties of a star determine its luminosity? a. distance and diameter b. temperature and distance c. temperature and diameter *d. apparent magnitude and temperature 6. How do we know that giant stars are larger in diameter than the Sun? *a. They are more luminous but have about the same temperature. b. They are less luminous but have about the same temperature. c. They are hotter but have about the same luminosity. d. They are cooler but have about the same luminosity. 7. Sirius A and B are two stars at the same distance from the Earth. In this binary system, Sirius A is much brighte *a. Sirius B must be much smaller than Sirius A. b. Sirius B must be much larger than Sirius A. c. Sirius B must be much more massive than Sirius A. d. Sirius B must be much less massive than Sirius A. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

8. In a Hertzsprung-Russell diagram, where are the stars with the smallest radius found? a. in the upper left corner b. in the upper right corner *c. in the lower left corner d. in the lower right corner 9. In a Hertzsprung-Russell diagram, where are 90 percent of all the stars found? a. in the giant region b. in the supergiant region c. on the dwarf sequence *d. on the main sequence 11. The star named Sheat is of spectral type M2 and luminosity class II. Based on this information, how does She *a. Sheat is cooler and larger than the Sun. b. Sheat is cooler and smaller than the Sun. c. Sheat is hotter and more luminous than the Sun. d. Sheat is hotter and larger than the Sun. 12. The star named Circini has the spectral type and luminosity class of O 8.5 V. Based on this information, how a. Circini is cooler and larger than the Sun. b. Circini is cooler and smaller than the Sun. *c. Circini is hotter and more luminous than the Sun. d. Circini is hotter and less luminous than the Sun. 13. Where are red giant stars found in the Hertzsprung-Russell diagram? *a. above the main sequence b. below the main sequence c. on the lower main sequence d. on the upper main sequence Table 2 Star Parallax (sec of arc) Spectral Type δ Cen 0.026 B2 IV HR 4758 0.05 G0 V HD 39801 0.005 M2 I 9 CMa 0.4 A1 V Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

14. Which star in the table is the closest to Earth? a. δ Cen b. HR 4758 c. HD 39801 *d. 9 CMa 15. Which star in the table has the highest surface temperature? a. δ Cen b. HR 4758 c. HD 39801 *d. 9 CMa 16. Which star in the table has the largest diameter? a. δ Cen b. HR 4758 *c. HD 39801 d. 9 CMa 1. The parsec is defined so that a star at a distance of 1 parsec has a parallax of one arcsecond. If a star has a para distance? a. 2 parsecs b. 5 parsecs c. 20 parsecs *d. 50 parsecs 2. The parsec is defined so that a star at a distance of 1 parsec has a parallax of one arcsecond. If a star has a para a. 2 parsecs b. 5 parsecs *c. 20 parsecs d. 50 parsecs 3. The parsec is defined so that a star at a distance of 1 parsec has a parallax of one arcsecond. If a star is located *a. 0.1 arcseconds b. 0.01 arcseconds c. 1 arcsecond d. 10 arcseconds Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

4. The parsec is defined so that a star at a distance of 1 parsec has a parallax of one arcsecond. If a star is located a. 0.25 arcseconds *b. 0.025 arcseconds c. 0.04 arcseconds d. 0.05 arcseconds 5. How do humans use their eyes to measure relative distance by parallax? a. By continuously focusing our eyes on distant objects, we can determine distance. *. b. Since our eyes are separated, the brain interprets the relative look angles of the two eyes in terms of dist c. Our eyes can measure the time it takes light to travel from an object, and from this we get distance. d. As we move our heads from side to side, our brain compares angles from each of these positions to work o 7. What would make parallax easier to measure? *a. the Earth's orbit being larger b. the stars being farther away c. the Earth moving faster along its orbit d. stars moving faster in their orbits 8. If two stars are emitting the same amount of light, how will the star that is farther away appear? a. brighter *b. dimmer c. redder d. bluer 9. What is absolute visual magnitude? a. the luminosity of a star observed from Earth b. the luminosity of a star observed from a distance of 1000 parsecs *c. the apparent magnitude of a star observed from a distance of 10 parsecs d. the apparent magnitude of a star observed from Earth 10. Absolute magnitude is defined as the apparent magnitude that a star would have if observed at a distance of 3 *a. It would be less than +5. b. It would be exactly +5. c. It would be greater than +5. d. More information on the star’s luminosity would be required to answer this question. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

11. What aspect of a star is a measure of the total energy radiated by the star in one second? a. apparent visual magnitude b. luminosity class c. spectral type *d. luminosity 12. Which stars have a large positive absolute magnitude? a. stars of high luminosity *b. stars of low luminosity c. nearby stars d. distant stars 13. If you compare two stars, which one will always have the greater luminosity? a. The one with the larger radius will always have the greater luminosity. b. The one with the higher surface temperature will always have the greater luminosity. *c. The one with the smaller absolute magnitude will always have the greater luminosity. d. The one with the largest distance will always have the greater luminosity. 14. The nearest star, Proxima Centauri, is about four light-years away and has a luminosity about 0.001 times tha *a. twice as bright b. four times as bright c. 16 times as bright d. 4000 times as bright 15. How does a star’s surface temperature determine the appearance of its spectrum? a. Surface temperature affects which elements are solid, liquid, or gaseous. b. Surface temperature determines the luminosity of the star. c. Surface temperature affects which elements can escape from the surface of the star. *d. Surface temperature determines the velocity of collision rates of atoms and ions. 16. What is the most accurate way to determine the surface temperature of a star? *a. Study the pattern of absorption lines from various atoms. b. Study the relative intensities of light measured through different photometric filters. c. Study the peak wavelength of the star's continuum blackbody spectrum. d. Study the pattern of emission lines on the star's spectrum. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

17. Which of the following can the strength of spectral lines tell you about a star? a. the radius b. the distance *c. the temperature d. the visual magnitude 18. You observe medium hydrogen Balmer lines, as well as neutral helium spectral features, in a star. What is the a. G b. M c. F *d. B 19. You observe medium hydrogen Balmer lines, as well as neutral helium spectral features, in a star. What is the a. 3000 K b. 10 000 K *c. 20 000 K d. 5500 K 20. What is the spectral sequence in order of decreasing temperature? *a. OBAFGKM b. OBAGFKM c. BAGFKMO d. ABFGKMO 1. Stars with masses below a certain threshold produce most of their energy via the proton-proton chain. What is a. 0.01 solar masses b. 0.1 solar masses *c. 1.1 solar masses d. 11 solar masses 2. Which of the following is considered to be the best explanation for the missing solar neutrinos? a. The Sun is fusing helium but not hydrogen. b. Nuclear reactions do not produce neutrinos as fast as theory predicts. c. The Sun may contain matter we haven't yet identified. *d. Neutrinos may oscillate between three different flavours. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

3. How did observations at the Sudbury Neutrino Observatory solve the solar neutrino problem? *a. They showed that the “missing neutrinos” had changed into a different type. b. They showed that other experiments had miscounted the number of solar neutrinos. c. They showed that models for the number of neutrinos produced by the Sun were wrong. d. They showed that neutrinos were not escaping from the core of the Sun. 4. Why does the main sequence have a limit at the lower end? a. Low mass stars form from the interstellar medium very rarely. b. Low mass objects are composed primarily of solids, not gases. c. The lower limit represents a star with zero radius. *d. A minimum temperature is required for hydrogen nuclear fusion to take place. 5. Why is there a main sequence mass-luminosity relation?  a. because helium fusion produces carbon  *b. because more massive stars support their larger weight by making more energy  c. because the helium flash occurs in degenerate matter  d. because all stars on the main sequence have about the same radius 6. What is the approximate mass of the lowest mass object that can initiate the thermonuclear fusion of hydrogen *a. 0.08 solar mass b. 1 solar mass c. 8 solar masses d. 80 solar masses 7. Which of the following is most similar in size to a brown dwarf? *a. the planet Jupiter b. a red dwarf c. a white dwarf d. a Bok globule Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

8. Which of the following are star-like objects that contain less than 0.08 solar masses and will never raise their c *a. brown dwarfs b. Herbig-Haro objects c. Bok globules d. T Tauri stars 9. What would happen if the nuclear reactions in a star began to produce too much energy? a. The star would shrink. *b. The star would expand. c. The star would collapse. d. Nothing would happen. 10. How much of its lifetime does the average star spend on the main sequence? a. 1% b. 10% c. 20% *d. 90% 11. The lower edge of the main-sequence band represents the location in the H-R diagram at which stars begin th *a. the zero-age main sequence b. the birth line c. the Coulomb barrier d. the evolutionary track Main Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

12. On the H-R diagram, the line indicates the location of the main sequence. Which of the four labeled locations a. 1 b. 2 *c. 3 d. 4 Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

13. Refer to the H-R diagram. Which point represents a star in which the proton-proton chain is occurring? a. 1 b. 2 *c. 3 d. 4 14. The Sun has an expected main-sequence lifetime of about 10 10 years. What is the lifetime on the main sequen a. 1.8×10 6 years *b. 1.8×10 9 years c. 1.8×10 10 years d. 1.8×10 11 years 16. What type of star is our Sun? a. intermediate-mass star b. yellow giant *c.low-mass star d. high-mass star 17. What is the lifetime of a 10 solar mass star on the main sequence? *a. 3.2×10 7 years b. 1×10 9 years c. 1×10 11 years d. 3.2×10 12 years 18. What characteristic of a star primarily determines its location on the main sequence? a. age b. distance from the galactic centre *c. mass d. radius 19. In which option below are the stellar types sorted from shortest to longest main-sequence lifetime? *a. O, A, K, M b. A, B, F, G c. K, F, B, O d. B, A, M, G 20. Consider two stars of the same mass: star 1 has just moved on to the main sequence, and star 2 is about to lea a. Star 2 has more helium in its core and a hotter surface. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

19. In which option below are the stellar types sorted from shortest to longest main-sequence lifetime? *a. O, A, K, M b. A, B, F, G c. K, F, B, O d. B, A, M, G 20. Consider two stars of the same mass: star 1 has just moved on to the main sequence, and star 2 is about to lea a. Star 2 has more helium in its core and a hotter surface. *b. Star 2 has more helium in its core and a cooler surface. c. Star 1 is more luminous and has a hotter surface. d. Star 1 is more luminous and has a cooler surface. 1. Which of the following relationships is the key to nuclear reactions in a star’s core remaining under control? a. Luminosity depends on mass. *b. Pressure depends on temperature. c. Density depends on mass. d. Weight depends on temperature. 2. What is opacity? a. the balance between the pressure and force of gravity inside a star b. the force that binds protons and neutrons together to form a nucleus c. the temperature and density at which a gas will undergo thermonuclear fusion *d. a measure of the resistance to the flow of radiation (photons) through a gas 3. What causes the outward gas pressure that balances the inward pull of gravity in a main-sequence star? a. the rapid outward flow of gas b. the rapid inward flow of gas *c. the high temperature and density of the gas d. the low mass of helium nuclei 4. Why is convection important in stars? a. because it mixes the star’s gases and increases the temperature of the star *b. because it mixes the star’s gases and transports energy outwards c. because it carries energy toward the core of the star d. because it carries the neutrinos to the surface of the star where they can escape Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

5. How does the temperature inside a star determine how energy flows inside it? a. The radiation rate depends on temperature. *b. The dependence of opacity on temperature makes convection happen. c. The dependence of opacity on temperature makes conduction happen. d. The temperature determines how much energy is produced at each layer. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

6. Which of the following is the best example of energy transport by conduction? a. Your feet are warmed when you hold them in front of a fire. b. Your feet are warmed when you wear socks. *c. Your feet get cold when you stand on a cold floor. d. Your feet get cold when you hold them over a cool air vent. ANSWER: 7. What does solving equations on a computer have to do with making a stellar model? *a. The equations apply the laws of stellar structure at locations within the star. b. Equations can describe the H-R diagram and a star’s location on it. c. The mass-luminosity equation tells you how to find a star’s luminosity given its mass. d. Equations are used to model the nuclear reactions inside a star. 8. What does the strong force do? a. It binds electrons to the nucleus in an atom. b. It holds the Moon in orbit around the Earth. c. It creates the magnetic field associated with sunspots. *d. It binds protons and neutrons together to form a nucleus. 9. What concept explains why both fusion and fission release energy? a. proton-proton chain energy b. Coulomb barrier energy c. strong force energy *d. nuclear binding energy 10. What is the name of the process by which the Sun turns mass into energy? a. nuclear fission *b. nuclear fusion c. convection d. radiation 11. While on the main sequence, what is a star’s primary energy source? *a. nuclear fusion b. nuclear fission c. gravitational potential energy d. magnetic fields Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

13. Why do nuclear fusion reactions only take place in the interior of a star (rather than at the surface)? a. The magnetic fields are strongest there. *b. The temperature and density are highest in the centre. c. The core is the only place where hydrogen is found. d. The strong nuclear force is only active in the centers of stars. 14. What is produced in the proton-proton chain? a. two hydrogen nuclei, a single helium nucleus, and energy in the form of visible light b. four hydrogen nuclei and energy in the form of gamma rays *c. a helium nucleus and energy in the form of gamma rays d. two hydrogen nuclei and energy in the form of visible light 15. What happens in the proton-proton chain? a. Two protons are fused to make a helium nucleus. b. Three protons are fused to make a lithium nucleus. c. A helium nucleus is split into four protons. *d. Four protons are fused to make a helium nucleus. 16. What is the term for the process that fuses hydrogen into helium in the cores of massive main-sequence stars? *a. the CNO cycle b. the proton-proton chain c. hydrostatic equilibrium d. the neutrino process 17. What happens in the carbon-nitrogen-oxygen (CNO) cycle? a. Carbon nuclei are split 3 ways to make helium nuclei. b. Carbon and oxygen combine to form nitrogen, which produces energy. c. Carbon and nitrogen combine to form oxygen and energy. *d. Four hydrogen nuclei combine to form one helium nucleus and energy. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

18. Stars with masses below a certain threshold produce most of their energy via the proton-proton chain. What is a. 0.01 solar masses b. 0.1 solar masses *c. 1.1 solar masses d. 11 solar masses 19. Which of the following is considered to be the best explanation for the missing solar neutrinos? a. The Sun is fusing helium but not hydrogen. b. Nuclear reactions do not produce neutrinos as fast as theory predicts. c. The Sun may contain matter we haven't yet identified. *d. Neutrinos may oscillate between three different flavours. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

20. How did observations at the Sudbury Neutrino Observatory solve the solar neutrino problem? *a. They showed that the “missing neutrinos” had changed into a different type. b. They showed that other experiments had miscounted the number of solar neutrinos. c. They showed that models for the number of neutrinos produced by the Sun were wrong. d. They showed that neutrinos were not escaping from the core of the Sun 1. As a star exhausts the hydrogen in its core, what happens? a. It becomes hotter and more luminous. b. It becomes hotter and less luminous. c. It becomes cooler and less luminous. *d. It becomes cooler and more luminous. 2. When does a star experience helium fusion? a. just before it enters the main sequence b. after it has become a red giant star *c. when it is on the horizontal branch d. before it leaves the main sequence 3. Why are giant and supergiant stars rare? *a. The giant and supergiant stages are very short. b. The star blows up before the giant or supergiant stage is reached. c. They do not form as often as main sequence stars. d. The giant or supergiant stage is very long. 4. Which of the following statements best describes why stars eventually die? a. Their lifespan is limited. *b. They exhaust all their fuel. c. Their cores become hotter. d. They become less luminous. 5. Which of the following occurs during the giant stage? *a. helium fusion in the core and hydrogen fusion in the surrounding shell b. hydrogen fusion in the core and helium fusion in the surrounding shell c. hydrogen and helium fusion in the core d. hydrogen flash 6. In what way are giants and supergiants similar? a. They are the main sequence stars. b. They undergo a helium flash stage as they enter the main sequence. *c. They are very luminous. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

1. What is the term for a collection of 105 to 106 old stars in a region 30 to 100 light-years in diameter? a. Herbig-Haro object *b. globular cluster c. open cluster d. giant cluster 2. What is the defining characteristic of stars within a cluster that are at the turnoff point? *a. They are just leaving the main sequence. b. They are just becoming white dwarfs. c. They are just entering the main sequence. d. They are about to explode in supernovae. Cluster 3. What is the approximate age of the star cluster in the H-R diagram? (Hint: Main sequence stars of spectral types O and B have a core supply of hydrogen that is sufficient to last about 250 million years; types A and F, about 2 billion years; type G about 10 billion years; types K and M about 30 billion years. The apparent magnitude scale means that larger numbers are toward the bottom of the vertical axis.) a. 200 million years b. 2 billion years *c. 10 billion years d. 30 billion years 4. Refer to the H-R diagram. How would the H-R diagram of a more distant star cluster look different? *a. The points would shift down, because all of the stars would have larger apparent magnitudes. b. The points would shift to the right, because all of the stars would appear to be cooler. c. The points would shift up, because all of the stars would have smaller apparent magnitudes. d. The points would shift to the left, because all of the stars would appear to be hotter. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

5. Which nuclear fuels does a one solar mass star use over the course of its entire lifespan? a. hydrogen *b. hydrogen and helium c. hydrogen, helium, and carbon d. hydrogen, helium, carbon, and oxygen 6. What is the ultimate fate of our Sun? a. It will become a neutron star. b. It will explode in a supernova. *c. It will become a white dwarf. d. It will explode in a nova. 7. Which of the following is the most important factor that determines a life cycle of a star (for example, why some stars have a short life span)? *a. mass b. temperature c. luminosity d. radius 8. What principle explains why matter flowing from one star in a binary system to its companion forms an accretion disk? a. conservation of tidal forces b. conservation of temperature *c. conservation of angular momentum d. conservation of energy 9. Suppose you discover a binary star system with a 0.7 solar mass giant star and a 2 solar mass main sequence star. Why is this surprising? a. 0.7 solar mass stars are not expected to become giants. b. All 2 solar mass stars should have left the main sequence. c. Giant stars are expected to destroy their companions, so the 2 solar mass star shouldn’t exist. *d. The 2 solar mass star should have become a giant before the 0.7 solar mass star. 10. When material expanding away from a star in a binary system reaches the edge of its Roche lobe, what happens? a. The material will start to fall back toward the star. b. All of the material will accrete on to the companion. *c. The material will no longer be gravitationally bound to the star. d. The material will increase in temperature and eventually undergo thermonuclear fusion. 11. When mass is transferred toward a white dwarf in a binary system, the material forms a rapidly growing whirlpool of material. What is that whirlpool called? *a. an accretion disk b. an Algol paradox Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

c. a planetary nebula d. a supernova remnant 12. Under what conditions are Type Ia supernovae believed to occur? a. when the core of a massive star collapses *b. when a white dwarf exceeds the Chandrasekhar-Landau limit c. when hydrogen detonation occurs d. when neutrinos in a massive star form a shock wave that explodes the star 13. Which of the following is almost always associated with a nova? a. a very massive star b. a star undergoing helium burning c. a white dwarf in a close binary system *d. a solar-like star that has exhausted its hydrogen and helium 14. Why can’t massive stars generate energy through iron fusion? a. because iron fusion requires very high density b. because no star can get hot enough for iron fusion *c. because both fusion and fission of iron nuclei absorb energy d. because massive stars go supernova before they create an iron core 15. If the hypothesis that novae occur in close binary systems is correct, then which of the following should novae do? a. They should produce synchrotron radiation. b. They should occur in regions of star formation. c. They should all be visual binaries. *d. They should repeat after some interval. 16. Why is the material that accretes onto a neutron star or black hole expected to emit X-rays? a. The material contains magnetic fields that will produce synchrotron radiation. b. Hydrogen nuclei begin to fuse and emit high energy photons. *c. The material will become hot enough that it will radiate most strongly at X-ray wavelengths. d. As the material slows down it converts thermal energy to gravitational potential energy. 17. What is the term for the form of electromagnetic radiation produced by rapidly moving electrons spiralling through magnetic fields? a. Lagrangian radiation b. ultraviolet radiation *c. synchrotron radiation d. infrared radiation 18. What type of object is the Crab nebula? a. a planetary nebula b. an open cluster c. an absorption nebula Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

*d. a supernova remnant 19. In the year 1054 CE, Chinese astronomers observed the appearance of a new star. What occupies that location now? a. a molecular cloud b. a planetary nebula with a white dwarf in the centre *c. a supernova remnant with a pulsar in the centre d. nothing 20. What produces synchrotron radiation? a. objects with temperatures below 10,000 K *b. high-velocity electrons moving through a magnetic field c. cold hydrogen atoms in space d. helium burning in a massive star 21. Where is synchrotron radiation produced? a. in planetary nebulae b. in the outer layers of red dwarfs c. in the collapsing iron cores of massive stars *d. in supernova remnants 22. What does the explosion of a type II supernova typically leave behind? a. It leaves behind a planetary nebula. b. It leaves behind a shell of hot, expanding gas with a white dwarf at the centre. *c. It leaves behind a shell of hot, expanding gas with a pulsar at the centre. d. Nothing is ever left behind. 23. Which of the following offered support for the theory that the collapse of a massive star’s iron core produces neutrinos? *a. the detection of neutrinos from the supernova of 1987 b. the brightening of supernovae a few days after they are first visible c. underground counts of solar neutrinos d. laboratory measurements of the mass of the neutrino 24. If you were to land on a neutron star, how would your mass change compared to your mass on the Earth? a. It would increase a lot. b. It would decrease a lot. c. It would increase a little. *d. It would remain the same. 1. What is the term for a collection of 105 to 106 old stars in a region 30 to 100 light-years in diameter? a. Herbig-Haro object Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

*b. globular cluster c. open cluster d. giant cluster 2. What is the defining characteristic of stars within a cluster that are at the turnoff point? *a. They are just leaving the main sequence. b. They are just becoming white dwarfs. c. They are just entering the main sequence. d. They are about to explode in supernovae. Cluster 3. What is the approximate age of the star cluster in the H-R diagram? (Hint: Main sequence stars of spectral types O and B have a core supply of hydrogen that is sufficient to last about 250 million years; types A and F, about 2 billion years; type G about 10 billion years; types K and M about 30 billion years. The apparent magnitude scale means that larger numbers are toward the bottom of the vertical axis.) a. 200 million years b. 2 billion years *c. 10 billion years d. 30 billion years 4. Refer to the H-R diagram. What type of star do the two data points above spectral type “A” represent? a. massive main sequence stars b. massive supergiant stars *c. white dwarfs with mass less than the sun’s mass d. white dwarfs with mass greater than twice the sun’s mass 5. Refer to the H-R diagram. What type of star do the data points above spectral type “M” represent? a. massive main sequence stars *b. main sequence stars with mass less than the sun’s mass c. main sequence stars with luminosities higher than the sun’s luminosity Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

d. pre-main sequence stars 6. Refer to the H-R diagram. How would the H-R diagram of an older star cluster look different? a. The points would shift to the right, because all of the stars would have lower temperatures. *b. The lower main sequence would look the same, but the turnoff would be at spectral type K or M. c. The points would shift down, because all of the stars would have lower luminosities. d. The lower main sequence would look the same, but the turnoff would be at spectral type F or A. 7. Refer to the H-R diagram. How would the H-R diagram of a more distant star cluster look different? *a. The points would shift down, because all of the stars would have larger apparent magnitudes. b. The points would shift to the right, because all of the stars would appear to be cooler. c. The points would shift up, because all of the stars would have smaller apparent magnitudes. d. The points would shift to the left, because all of the stars would appear to be hotter. 8. Which nuclear fuels does a one solar mass star use over the course of its entire lifespan? a. hydrogen *b. hydrogen and helium c. hydrogen, helium, and carbon d. hydrogen, helium, carbon, and oxygen 9. Star A is a 1 solar mass white dwarf, and star B is a 1.3 solar mass white dwarf. How would they differ? a. Star A has a smaller radius. *b. Star B has a smaller radius. c. Star B is supported by neutron degeneracy pressure. d. Star A is hotter. 10. What is the source of the energy radiated by a white dwarf? a. the proton-proton chain b. the CNO cycle c. gravitational contraction after becoming a white dwarf *d. gravitational contraction during the white dwarf formation phase 11. What does the Chandrasekhar-Landau limit tell us? a. Accretion disks can grow hot through friction. b. Neutron stars of more than 3 solar masses are not stable. *c. White dwarfs more massive than 1.4 solar masses are not stable. d. Stars with a mass less than 0.5 solar masses will not go through helium flash. 12. What is the ultimate fate of our Sun? Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

a. It will become a neutron star. b. It will explode in a supernova. *c. It will become a white dwarf. d. It will explode in a nova. 13. Which scenario is most likely to happen when the Sun enters the red giant stage? *a. Mercury, Venus, and Earth will be destroyed by the expanding Sun. b. Mercury will be destroyed by the expanding Sun, but Venus and Earth will remain intact. c. The Sun will engulf and destroy all planets in the Solar System. d. The Sun will never expand far enough to reach Mercury or any other planets in the Soar System. 14. If the stars at the turnoff point of a cluster have a mass of 3 times the mass of the Sun, what is the age of the cluster? *a. 6.4×108 years b. 3.3×109 years c. 3.0×1010 years d. 1.6×1011 years 15. Which of the following correctly describes a relationship between pressure, temperature, and density in degenerate matter? a. Pressure depends only on the temperature. *b. Pressure does not depend on temperature. c. Temperature depends only on density. d. Pressure does not depend on density. 16. What is a white dwarf composed of? a. hydrogen nuclei and degenerate electrons b. helium nuclei and normal electrons *c. carbon and oxygen nuclei and degenerate electrons d. degenerate iron nuclei 17. As a white dwarf cools, its radius remains the same. Why is this? a. because pressure due to nuclear reactions in a shell just below the surface keeps it from collapsing *b. because pressure does not depend on temperature for a white dwarf, since the electrons are degenerate c. because pressure does not depend on temperature, since the star has exhausted all its nuclear fuels d. because material accreting onto it from a companion maintains a constant radius 18. What are the two longest stages in the life of a one solar mass star? a. protostar, pre–main sequence b. protostar, white dwarf c. protostar, main sequence *d. main sequence, white dwarf Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

19. Which of the following is the most important factor that determines a life cycle of a star (for example, why some stars have a short life span)? *a. mass b. temperature c. luminosity d. radius 1. A Black Hole has mass M BH = 15 M Solar . What is its Schwarzschild radius? a. 50.5 km *b. 44.24 km c. 76 km d.100 km 2. A Black Hole has mass M BH = 1800 M Solar . What is its Schwarzschild radius? a. 150.5 km b. 444.24 km *c. 5309.32 km d.8769.60 km 3. If the Schwarzschild radius of a Black Hole is 10 km, what is its mass? a. 15 M solar b. 6.8 M solar *c. 35 M solar d. 48 M solar 4. Why black holes are black? a. Because they do not have any energy b. Because nothing escapes c. Because radiation does not escape *d. Because light does not escape 5. What is at the center of a black hole? a. Another black hole b. A little galaxy *c. The singularity point d. An X-ray source 6. What is a supermassive black hole? a. Black hole with mass similar to the sun b. Black hole with mass similar to Jupiter c. Black hole with mass similar to 3 M solar *d. Black hole with mass (thousand - billion) M solar 7. How did the Black Holes were predicted Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

a. By observation b. With radio telescopes c. With optical telescopes *d. Mathematically using Einstein’s general relativity theory 8. Hawking radiation is black body radiation due to a. Electromagnetic effects *b. Quantum effects c. Gravity effects d. Mechanical effects 9. Where is the Hawking radiation emitted? a. Near the singularity *b. Near the horizon c. Near the Schwarzschild radius d. From particles orbiting the black hole 10. BONUS QUESTION Two Black Holes have the following masses M 1 = 100 M solar and M 2 = 40 M solar . Show that Schwarzschild radius of the first black hole satisfies the relation . (Do not panic this is a really easy question!!. Hint: All you need is the relation that gives the Schwarzschild radius of a black hole. Look at the lecture slides.) Old But Good Astronomy Astronomy is the oldest of the sciences. Humans have always looked to the sky, and wondered, and thought, and looked again, and said "hmmm...that's funny" (remember I. Asimov from the quote in the Introduction?) and formulated theories and measured again and made better instruments and recalculated and reformulated — and so on. Of course, astronomy was always mixed up with religion — the gods were "up there" and we - mere mortal human beings - were "down here", although man was, after all, at the centre of the universe — make no mistake about that! The Sun god (known by various names) raced across the sky each day, keeping a watch on us. The Moon god kept tabs on us by night (well, not every night — and wasn't that a little confusing). Then, there were the planet gods, obviously lesser gods, farther away and not always in the night sky (where were they during the day?) Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

The Sun, Moon and planets previously mentioned were so important that the days of the week are actually named after the seven visible objects that have been seen, recorded and named for centuries. In the table shown below it is quite clear how the known heavenly objects, listed by both their current English names and their old Teutonic names correspond to today’s English names of the days. The names of days in French and Spanish are remarkably close to each other and you can certainly see the connection with their English counterparts. Heavenly Body Teutonic Name English Name French Name Spanish Name Sun Sun Sunday dimanche domingo Moon Moon Monday lundi lunes Mars Tiw Tuesday mardi martes Mercury Woden Wednesday mercredi miércoles Jupiter Thor Thursday jeudi jueves Venus Fria Friday vendrdi viernes Saturn Saturn Saturday samedi sábado Ancient peoples had various ways of keeping track of time on a daily, or even a weekly, basis but what is particularly interesting is how some peoples kept track of time throughout the year. The most obvious and best-known device is Stonehenge, located in the south of England. One of the great mysteries of this structure lies in the construction itself — just how was this accomplished? It was built over a relatively long time (1200 years from about 2750 BC to about 1550 BC) — see the pictures here. This lower picture gives us another view of Stonehenge (from the ground). The inset shows sunrise on the summer solstice as seen from the centre of the stone circle rising over the Heel Stone. Explanation: Stonehenge, four thousand year old monument to the Sun, provides an appropriate setting for this delightful snapshot of the Sun's children gathering in planet Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Earth's sky. While the massive stone structure dates from around 2000 B.C., this arrangement of the visible planets was recorded on the evening of May 4th, 2002 A.D. Bright Jupiter stands highest above the horizon at the upper left. A remarkable, almost equilateral triangle formed by Saturn (left), Mars (top), and Venus (right) is placed just above the stones near picture center. Fighting the glow of the setting sun, Mercury can be spotted closest to the horizon, below and right of the planetary triad. Who Built Stonehenge? The question of who built Stonehenge is largely unanswered, even today. The monument's construction has been attributed to many ancient peoples throughout the years, but the most captivating and enduring attribution has been to the Druids. This erroneous connection was first made around three centuries ago by the antiquary, John Aubrey. Julius Caesar and other Roman writers told of a Celtic priesthood that flourished around the time of their first conquest (55 BC). By this time, though, the stones had been standing for 2,000 years, and were, perhaps, already in a ruined condition. Besides, the Druids worshipped in forest temples and had no need for stone structures. The best guess seems to be that the Stonehenge site was begun by the people of the late Neolithic period (around 3000 BC) and carried forward by people from a new economy that was arising at this time. These "new" people, called Beaker Folk because of their use of pottery drinking vessels, began to use metal implements and to live in a more communal fashion than their ancestors. Some think that they may have been immigrants from the continent, but that contention is not supported by archaeological evidence. It is likely that they were indigenous people doing the same old things in new ways. Other Interesting Early Structures Other spectacular (for their period) constructions include the Templo Mayor, situated near the present-day Mexico City, constructed by the Aztec empire, and the Mayan cities of Chichén Itzá and Tulum (on the Yucatan coast near Cancun). Here is a scale model of Templo Mayor, one of the main temples in the ancient city of Tenochtitlan (now Mexico City). See the Wikipedia entry for Templo Mayor for more information. These remarkable structures always had some link with solstices and equinoxes as a focal point, demonstrating a strong working knowledge of serious astronomy. Possibly the best known construction on the Chichén Itzá site is Kukulcan's Pyramid. El Castillo (Kukulkan -Quetzalcoatl), a square-based, stepped pyramid that is approximately 75 feet tall. This pyramid was built for astronomical purposes and during the vernal equinox (March 21) and the autumnal equinox (September 21) at about 3 P.M. the sunlight bathes the western balustrade of the pyramid's main stairway. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

This causes seven isosceles triangles to form imitating the body of a serpent 37 yards long that creeps downwards until it joins the huge serpent's head carved in stone at the bottom of the stairway. Mexican researcher Luis El Arochi calls it "the symbolic descent of Kukulcan" (the feathered serpent), and believes it could have been connected with agricultural rituals. A North American site often mentioned is the Big Horn Medicine Wheel (Wyoming, USA), a much simpler version of Stonehenge, consisting of rocks strategically placed on the ground in the form of a giant wheel with spokes aligned with the rising and setting of the Sun (on equinoxes and solstices), Moon and bright stars. Lunar Cycles Most ancient civilizations paid particular attention to the 29.5-day lunar cycle and formulated calendars based on this length of time. Remember the word "month" is obviously derived from the word "moon". Because our year of 365 days is not an even multiple of 29.5 the dates of the lunar phases vary from year to year. However, the fact that 19 calendar years is almost exactly 235 lunar months means that we get the same lunar phases on about the same dates every 19 years, a fact recognized as long ago as 432 BC when Greek Mike Meton (well, at least his last name was Meton!) realized this and now we refer to this lunar cycling as the Metonic cycle (the Jewish calendar follows this cycle). The date for Easter varies annually (unlike Christmas which always falls on December 25 — a little known fact!!!) and is related to the lunar cycle. Easter Sunday is always the Sunday following the first full moon after the spring equinox. The Metonic cycle is not to be confused with the saros cycle, which has to do with the cycle of eclipses (so many cycles — and not one to ride!). Above, I have highlighted three specific developments which display the interest in astronomy by ancient cultures:  Stonehenge in Europe (England)  Chichén Itzá in Mexico (Mayan)  Big Horn Medicine Wheel in the USA (Plains Indians). Other examples include Greek (Pleiades — more on that later), Incan (South American — Nazca desert — pictures on various websites) and Polynesian (star positions for navigation throughout the vast island country). As well, the Chinese had a well developed, and at times superior, knowledge and use of astronomy ( supernova — explosion of a giant star — of 1054 AD). However, it was in the Middle East (Egypt, Mesopotamia (now Iran and Iraq) and Greece) that modern science developed and it is through here that our historical journey now takes us. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Many names come to mind when considering the enormous influence of the Greek empire on present-day science. Take a look at the timelines on pages 52 and 53 of the textbook (also shown below) for a visual representation of the early history of astronomy. Note the long Dark Ages break between Ptolemy to Copernicus. Once you have finished viewing the timeline, follow along with the lesson notes for more details. Thales of Miletus (624-547 BC) was one of the very early Greek scholars to promote the notion that the universe was rational and, therefore, understandable. Previous cultures in Egypt and Babylonia believed that the real causes of things were mysteries beyond human understanding. To Thales and his followers the mysteries of the world (and heavens, etc.) are so because they are unknown, not because they are unknowable. Pythagoras (570-500 BC), following from Thales' wisdom, believed that relationships in nature had developed in accordance with geometrical or mathematical relationships. His studies in musical acoustics led him to believe that the planets actually produced music as they traveled in their orbits, leading to the concept of the "music of the spheres". You’ve probably heard Pythagoras’ name before and, yes, he’s the same person who developed the so-called Pythagorean formula for right-angle triangles you learn about in high school mathematics. Socrates (470-399 BC), a seminal figure in Greek history, was more of a philosopher than a scientist (there weren't really any scientists, as we think of them, in these early Greek days) who talked a lot and wrote nothing, so what we know of him we know through lore and through his students (Plato being his chief biographer). He held that virtue is understanding and that no human being knowingly does wrong (now how about that for a teacher!). Socrates' method of philosophical inquiry consisted of questioning people on the positions they asserted and working them through questions into a contradiction, thus proving to them that their original assertion was wrong. Plato (428-348 BC) carried on the teachings of Socrates for most of his early life but actually took little interest in science although he thought that mathematics was a valuable discipline. Plato wrote the Republic , in which he formulated his ideas of the perfect state. According to the New Lexicon Webster's Dictionary Plato's greatest contribution was on his theory of "ideas", of which "love" is one which he describes as " as desire for union with the beautiful, ascending in a scale of perfection from human passion to ecstasy in the Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

contemplation of designating love for a person, usually of the opposite sex, that is free of carnal desire ", so-called Platonic love — now that's something to aspire to!! Aristotle (384-322 BC), a great Greek scholar and thinker, was a pupil of Plato (and a teacher of Alexander the Great) who really didn't get along with Plato or anybody else for that matter. Aristotle could not bring himself to think of the world in abstract terms (the way Plato did) — instead he believed that the world could be understood fundamentally through the detailed observation and cataloguing of phenomena — in other words, knowledge (which is what the word science means) is fundamentally empirical . Aristotle wrote on many subjects, including physics, mathematics, meteorology and, anatomy. Although much of what he wrote about science was wrong, we must recognize that he was not really a scientist; he was first and foremost a philosopher. Because of his writings and insight he became the great authority for almost 2000 years and, hence, a great influence on all thinking. Aristotle tried to understand the universe (not the universe as we know it today) by combining the most basic observations with first principles (ideas that he believed were obviously true; like the perfection of the heavens). He believed that the universe existed in two parts — Earth (corrupt and changeable) and the heavens (perfect and immutable). He also believed that the Earth was at the centre of the universe — another first principle. Aristotle developed the whole idea of inductive reasoning through learning what was known about a certain topic, gaining a consensus on the subject by talking to anyone and everyone, testing it thoroughly (although he was regarded as a know-it-all), and working out the underlying principles. This sequence of reasoning is now the basis of all Western scientific thinking, the so-called scientific method, which we will get to shortly. Another important figure in Greek science is Claudius Ptolemy (90- 168 AD, although these dates are approximate). He developed a model of the universe based on his observations and those of his forefathers which predicted fairly well planetary events of the future. One of the more serious issues that any model had to overcome was that of the retrograde motion of some of the planets. Ptolemy borrowed an idea from other scholars that put planets on “epicycles” or smaller circles around which they would travel as they orbited the Earth in perfect, larger circles (see below the picture of Ptolemy) Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

BUT, the model utilized one tenet which turned out to be the biggest flaw in the model — an Earth-centred universe. This concept (the Earth-centred universe) was so ingrained in all Western thinking, that it influenced the development of science for centuries. How could it possibly be any other way? Humanity just HAD TO BE at the centre of the universe, didn't we??? Let's review a few things : Early attempts to model the solar system and the universe belong to the Egyptians and the Greeks (around the time of Christ). Ptolemy (Greek) came up with his circular orbit/epicycle/Earth-centred model around 150 A.D. Nothing much happened for about 1400 years — the Dark Ages. All this time two things were particularly important for Church and science. First of all, not much science was done during these 1400 years and the Church held fast to the idea that: a the orbits of the planets, Sun and Moon were perfect circles — after all, they were heavenly bodies and as such their paths had to be perfect and nothing was more perfect than a circle, and b Earth was at the centre of the universe! Enter Nicolaus Copernicus (1473-1543) Copernicus was able to study astronomy by virtue of his education and family wealth. He reviewed current (at that time) naked-eye measurements and how they fit with the Ptolemaic model and decided to rethink the basic model by considering Aristarchus' notion of a Sun- centred solar system (an idea that was now some 1800 years old). Following consultation with other scholars and following his own inner urgings to make public his own ideas, he published a book entitled De Revolutionibus Orbium Caelestium in 1543 (Concerning the Revolutions of the Heavenly Spheres), in which he claimed that the true and accurate model of the solar system could only be that of a Sun-centred system. However, he still held that the orbits of the planets had to be circular (not ellipses as we now know) and, consequently, he had to make use of the same epicycle system that Ptolemy did with the result that the predictions of his model produced results that agreed no better with observations than Ptolemy's model. Three years after Copernicus' death a Dane, Tycho Brahe , was born (1546-1601). Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Tycho, as he has become known, was born into a respected and noble family, grew up as an arrogant child and teen and lost part of his nose in a fight, but became the greatest naked-eye observer of all time. He had always had an interest in astronomy and when he, as a young man, observed that the expected conjunction of Jupiter and Saturn was late by two days (based on Copernicus' model) decided to start compiling his own set of observations. Eventually, King Frederick II (Denmark) agreed to sponsor his work and set him up in his own spectacular observatory, on his own island of Hven in the Baltic Sea, where he did his work. Despite all this, he failed to come up with any better models of planetary motion. Just before Tycho's death he engaged a young German scholar Johannes Kepler (1571-1630), who showed great promise and who inherited Tycho's data. Kepler, a very religious man, sought to develop a new model of the solar system, but had great faith in Tycho's measurements and, after trying desperately to fit the observations of Mars's orbit with a circular orbit, decided to try something different. Try to imagine what Kepler's thought pattern might be. For centuries, scientists and philosophers had tried to fit observations to models using ideas (such as circular orbits) that were central to human beliefs. Kepler decided to try the reverse — throw out long- held beliefs and develop a model that fit observations — some claim this was the real birth of modern science. After all, this is precisely how we conduct science today — this is the scientific model (more on this shortly). So, Kepler published his three laws of planetary motion (the first two in 1609, the last in 1619). The laws go something like this: Kepler's First Law : The orbit of each planet around the Sun is an ellipse with the Sun at one focus. The diagram below shows what an ellipse is. An ellipse has two foci (plural of focus) and the Sun is at one focus (nothing is at the other focus). The major axis is a line drawn through the two foci and ending at each "end" of the ellipse. Half this distance is called the semi-major axis . The same holds true for the minor axis, perpendicular to the major axis. The ratio of the distance between the two foci to the major axis length is called the eccentricity . A circle has an eccentricity of zero (0.00) because the two foci are on top of each other. A straight line has an Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

eccentricity of unity (1.0) because the two foci are as far away from each other as they can possibly be – at infinity on either side of the ellipse. So, eccentricities vary from zero to one. The eccentricity of Venus' orbit is 0.007 (almost a circle) while that of Pluto is 0.248 — fairly eccentric (not unlike your Astronomy prof.!) Kepler's Second Law : As a planet moves around in its orbit, it sweeps out equal areas in equal times. As mentioned previously, when the planet is closer to the Sun (around its perihelion) it moves faster along its orbit than when close to the aphelion. In the diagram above the picture on the right shows this. The planet moves from A to B (around its aphelion, farthest from the Sun) in the same time that it takes to go from A’ to B’ (around its perihelion, closest to the Sun). The areas shaded in blue are equal. Kepler's Third Law : The squares of the periods of any two planets have the same ratio as the cubes of their semi-major axes. Mathematically, we can write this as p 2 = a 3 where p is the orbital period in years and a is the average distance from the Sun in AU. This is a remarkably simple relationship. When things work out this beautifully you just know it's right!! Here is a nice little animation (really a formula to demonstrate Kepler’s Third Law) that I would like you to play around with. The idea is to put a number in the square on either side of the equation and the value for the other side pops into place. For example, if you put in the number 1 (on either side) you will see that 1 appears in the other side; this is the information for Earth where clearly the orbital period is 1 year and the average distance from the Sun is 1 AU (because that’s how an AU is defined). Try the formula for other planets, such as Mercury ( p = 0.24 years and α = 0.39 AU) or Saturn ( p = 29.5 years and α = 9.58 AU). Please try other values found in Table A.6 in Appendix A in the textbook. flash animation http://astro.unl.edu/classaction/animations/renaissance/keplers_third. html So, there you have it. Kepler's three laws of planetary motion matched Tycho Brahe's measurements better by far than any other models. I want you to watch the following video about Kepler’s Laws. In this clip from Sagan’s COSMOS series (which starts in the middle of a Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

thought) quickly leads into Sagan’s brilliant commentary on Kepler’s discovery of his three laws of orbital motion. It is well worth watching. Kepler’s Laws (4:09 min.) video: <div class="player-unavailable"><h1 class="message">An error occurred.</h1><div class="submessage"><a href="http://www.youtube.com/watch?v=XFqM0lreJYw" target="_blank">Try watching this video on www.youtube.com</a>, or enable JavaScript if it is disabled in your browser.</div></div> www.bing.com/videos/search? q=kepler's+laws+videos&FORM=VIRE15#view=detail&mid=6AA900E8 C72CBB2824C56AA900E8C72CBB2824C5 However, there were still objections to the new model, all based on old beliefs, but soon all these objections would be met by yet another brilliant scientist. Enter Galileo Galilei (1564-1642), a contemporary of Kepler. We won't go into the details of Galileo's work to dispel the remaining objections to Kepler's work — they are detailed in the text very well. Among Galileo's great contributions to modern science was his development called the telescope (Hans Lippershey actually invented the telescope but only as a toy). He used the telescope for the first time in 1609-10 (thus, 2009 marked the 400th anniversary of Galileo’s first use of the telescope and that is why 2009 was the Year of Astronomy). Although Galileo was not the first to look at the sky using a telescope he was the one who used the telescope to open the heavens to mankind. Galileo observed more stars in the Milky Way than could be counted, four moons orbiting Jupiter, phases of Venus, and other heavenly phenomena. Concerning stars never before seen, Galileo wrote: “I had determined to depict the entire constellation of Orion, but I was overwhelmed by the vast quantity of stars and by want of time, and so I have deferred attempting this to another occasion, for there are adjacent to, or scattered among, the old stars more than five hundred new stars.” When he observed the irregular surface of the Moon he proved to himself, at least, that it was not perfect, as the Church had been teaching. However, it was his persistent viewing of Jupiter and its points of light, which turned out to be its moons as he soon realized, that sealed the fate of the Earth-centred Ptolemaic model of the solar system. That, along with his observations of Venus going through a complete set of phases that could only be explained if Venus revolved around the Sun, which proved to Galileo, and eventually the rest of the Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

world that the Sun-centred model was the correct one. Let’s look at Galileo’s observations of Venus to demonstrate more convincingly that what he saw demonstrated to him, and anyone else who cared to review his observations, that the Sun-centred model was the correct one. First, look at an animation demonstrating what Venus would look like if the Ptolemaic (Earth-centred) model was correct. flash animation http://astro.unl.edu/classaction/animations/renaissance/ptolemaic.ht ml . With this configuration you see that the Earth is in the centre. Venus orbits the Earth but on a circle of its own (called an epicycle) while the Sun orbits Earth beyond that. When you start the animation observe what Venus must look like from Earth (top right of picture) as Venus and the Sun orbit Earth. You see that Venus would always show just a crescent phase. Now, let’s view another animation demonstrating what Venus would look like if the Copernican (Sun-centred) model was correct. flash animation http://astro.unl.edu/classaction/animations/renaissance/venusphases. html Here you see the correct configuration with the Sun at the centre and Earth and Venus orbiting the Sun. When you start the animation you will see Venus going through its phases just as Galileo would have observed with his telescope. It goes through a full phase cycle just like the Moon, something possible only if the Sun is at the centre of the solar system. As mentioned above, Galileo observed Venus going through a complete set of phase exactly like the Moon’s phase cycle. The only possible scenario Galileo could conclude was that Venus must revolve around the Sun with an orbital radius smaller than Earth’s. Bingo! The revolution was complete. But what was it that "held" the planets in their orbits??? Galileo died on January 8, 1642 having failed to convince the leaders of the Roman Catholic Church that its interpretation of the Holy Scriptures was inconsistent with observed facts. The Church pronounced his findings false and heretical and forbade anyone to teach them and put Galileo under a form of "house arrest". Only recently was this position of the RC Church recanted (by Pope Jean Paul II) and a much overdue apology issued. So blind are the eyes of men when they do not want to see! Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Isaac Newton was born on December 25, 1642 . He was a sickly child who eventually attended Cambridge University (England) but returned to home in Woolsthorpe during the great plague of England. There he investigated mathematics, optics, motion and discovered gravity. Before we look at Newton's Law of Gravitation I must caution you that this law involves the concept of "force", something we have not yet dealt with (although we will study this later in this module). Basically, a force is either a push or a pull. In the case of a planet circling the Sun the idea is that something makes it do that, rather than travelling in a straight line. That is, without a "force" acting on the planet it would travel in a straight line. Because it travels in a circle (or ellipse) something must be pulling on it to make it follow this path. Newton cleverly realized that an invisible force must exist between two objects, called it "gravity", that it must be the same force which causes an apple to fall to the ground and the rest is history, so to speak. So, Newton's Universal Law of Gravitation, a real "tour de force" (HA!), is summed up nicely in the diagram shown below. This law shows that the gravitational force is proportional to the masses of both objects and inversely proportional to the square of the distance between the masses. This is mathematical jargon. What it really means is that if the mass of either object is doubled (say) then the force also doubles; if the mass is tripled then the force also triples, and so on. Also, if the distance between the masses doubles then the force diminishes by a factor of four (which is two squared — 2 x 2); or if the distance triples then the force diminishes by a factor of nine (three squared — 3 x 3), and so on. I've tried to explain this in simple terms; you may need to read this a few times to understand it, although it is fairly basic mathematics (think high school math). With this law Newton was able to derive Kepler's Laws and showed that they applied to any two bodies moving under the influence of gravity (not just planets) and that they orbited with the centre of mass at one focus. He was one smart dude! Furthermore, he showed that a few other orbital paths were possible. Elliptical orbits are bound or closed orbits which keep the two objects circling each other forever. Parabolic and hyperbolic orbits, unbound or open orbits, are also possible. Comets can be on either a bound elliptical orbit (returning to the Sun like clockwork) or on an unbound parabolic orbit (passing by the Sun only once before returning to the vast regions of outer space). The same applies to asteroids or other space objects. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Newton also derived Kepler's Third Law in a more generalized form which turned out to have a very useful outcome. It goes something like this: For any two masses, M 1 and M 2 , the formula for the period or orbit of either mass is given by P 2 = 4 π 2 a 3 /(G(M 1 +M 2 )) (G is the universal gravitational constant — a known, but empirical, value). If M1 is the mass of the Sun (M s ) and M 2 is the mass of a planet, say, then (M 1 + M 2 ) becomes M s , because the mass of the Sun is so much greater than the mass of the planet, and the formula now becomes P 2 = (4 π 2 /GM s ) a 3 The significance of this outcome is that we have developed the primary method of determining masses throughout the universe. You see, we can't weigh the Sun? So, we determine its mass by measuring both the orbital rate of a planet (P) and its average distance from the Sun (a) and then use the equation to determine the Sun's mass, viz. M s = 4 π 2 a 3 /GP 2 The same holds true for any two objects, one massive and the other a satellite (natural or otherwise). This little derivation is for information only – no need to memorize it, thank goodness. We determine the Earth's mass by observing the Moon. We determine Jupiter's mass by observing any of its moons. We can only determine a star's mass if we can find something in orbit around it. Tides A very nice application of Newton's Law of Gravitation is the study of tides. You will find this material in the textbook in section 3.5. On Earth, the oceans go through a daily cycle of tides that are explained by the gravitational influence of the Moon. The tides on Earth are mostly the result of the Moon’s gravitational pull on Earth. The Moon’s gravity pulls more strongly on the near side of the Earth than the far side and this difference is known as a tidal force. The tidal force, or difference between the force on the near side and the force on the far side, results in a bulge in the water (high tide) on both the Moon-facing side of Earth and the opposite side of the Earth. Of course, this also results in a low tide on the sides of the Earth at 90° to the near and far sides (see diagram below). So, as the Earth spins around on its axis any location on Earth experiences two high tides and two low tides every day. As shown in the diagram below, the side of the Earth facing the Moon feels a stronger (bigger) gravitational attraction than the side facing away from the Moon. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

As the Earth rotates "inside this bulge" it moves you through each of these two bulges once each day, thereby creating two high tides and, as a consequence, two low tides, as mentioned above. The tides do not occur at the same time each day, as this simplistic explanation suggests, because of the Moon's rotation around the Earth, adding about 50 minutes each day to the time of the tidal pattern. (recall that the lunar cycle is about 29.5 days so it takes the Moon about 24/29.5 hours/day = 0.81 hours/day = 49 minutes/day) The Sun can also bring about tides on Earth. Although it is much, much farther away than the Moon, its mass is considerably larger than the Moon's. It is really the difference in gravitational attraction from one side of the Earth to the opposite side that results in tides; still, the Sun does cause tiding. The effect of the Sun is particularly noticeable when the Sun, Moon and Earth are all lined up, as they are at a new and/or full Moon. At this time of the month, the tides are highest and are called spring tides (has nothing to do with the spring season) because the water "springs" up the shore. During first and third quarter Moons the tides are called neap tides because the Sun, now perpendicular to the line between the Earth and the Moon, tends to cancel out the effect of the lunar tides resulting in lower tides than at other times. Two interesting results of the Earth-Moon tides are that, due to tidal friction , the rotation of the Earth is gradually slowing down (the days are getting slightly longer) and the Moon is moving further from the Earth. These changes are very, very slight and would become noticeable over millions of years. Of course, in all of this, angular momentum is still conserved, although we have yet to learn what "angular momentum" is — that will come shortly. Tidal friction is believed to be the cause of the Moon's synchronous rotation with the Earth. Let’s now move on and learn about the scientific method. The Scientific Method: Deductive and Inductive Reasoning In science, knowledge progresses when we apply logical reasoning, devoid of emotion and personal desires, to the observations from the experiments that we execute. Two types of reasoning are utilized — deductive and inductive. "Deductive reasoning" refers to the process of concluding that something must be true because it is a special case of a general principle that is known to be true. For example, if you know the general principle that the sum of the angles in any triangle is always 180 degrees, and you have a particular triangle in mind, you can then conclude that the sum of the angles in your triangle is 180 degrees. Deductive reasoning is logically valid and it is the fundamental method in which mathematical facts are shown to be true. "Inductive reasoning" is the process of reasoning that a general principle is true because the special cases you've seen are true. For example, if all the people you've ever met from a particular town have been very strange, you might then say "all the residents of this town Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

are strange". That is inductive reasoning: constructing a general principle from special cases. It goes in the opposite direction from deductive reasoning. Consider the following example: Trump : Every time I kick a ball up, it comes back down, so I presume the next time I kick it up, it will come back down, too. Trudeau : That's because of Newton's Laws. Everything that goes up must come down (not unlike the stock market!). And so, if you kick the ball up, it must come down. Trump is using inductive reasoning , arguing from observation, while Trudeau is using deductive reasoning , arguing from the law of gravity. Trudeau's argument is clearly from the general (the law of gravity) to the specific (this kick). Trump's argument may be less obviously from the specific (each individual instance in which he has observed balls being kicked up and coming back down) to the general (the prediction that a similar event will result in a similar outcome in the future) because he has stated it in terms only of the next similar event—the next time he kicks the ball. The only reason we go through all of this is because the scientific method is based on both inductive and deductive reasoning and so we must be aware of both types of reasoning. The Scientific Method The basic idea of the scientific method, the cornerstone of modern science, is quite simple: one looks at a set of observations or demonstrated facts, develops a hypothesis that satisfies or predicts accurately the observations, makes further observations, tests the hypothesis and makes adjustments as necessary. The flow chart shown here is a good pictorial representation of the scientific method. Science and Nonscience Now that you have a pretty good idea of what science is, it is important to be aware of what science is not . Pseudoscience , or false science, is all around us. Lots of people make predictions based on reading tea leaves, tarot cards, palms, psychic determinations. Such so-called scientific prognostications have never met the "test of time" using the accepted scientific method. (We’ll come to "astrology" shortly) Nonscience (notice how close this word is to "nonsense") is a term used to describe predictions based on intuition, societal traditions (old wives’ tales), faith, political conviction, and tradition. However, such non-science techniques also do not meet the "test of time" and when made subject to the scientific method, simply fall apart. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Sometimes, scientists just make mistakes — a good example of this is the "cold fusion" proposals of some years ago. An interesting book has been published entitled When Bad Astronomy happens to Good People , by Philip Plait (John Wiley & Sons, 2002), and reviewed in October 2002 issue of Sky and Telescope. Astronomy is once again in a period of great growth and interest, perhaps its most remarkable, fastest-developing phase — in the past 10-15 years there have been startling developments:  Hubble telescope has brought us pictures of heavenly objects with a clarity never before seen  have viewed planets around other stars  have seen the births of galaxies at the very edge of the observable universe  discovered rings on all Jovian planets  discovered new moons on some Jovian planets  have found Pluto-sized Kuiper Belt objects  have found pulsars, quasars, and black holes (once thought to be a theoretical artefact), in fact, we now have evidence that black holes are at the centre of most galaxies  detected gravitational waves  Astrology  Let's take some time to talk somewhat about the practice of "astrology". In ancient times astronomy and astrology went hand-in-hand and many astronomers practiced astrology because it was important to their livelihood, even though most didn't believe a word of it.  Astrology holds that human events and even traits depend on the positions of the Sun, Moon, planets and star patterns at a person's birth. Important events in a person's history, or at any time that seems appropriate to the person "reading the heavens and predicting your future", were revealed by a certain heavenly alignment. And so on.  Recall the picture of the Sun and the constellations of the zodiac from Chapter 2, shown here again  Well, to put it bluntly, there is no scientific proof that "astrology is any more able to predict the past, present or future than you or I making random choices", to paraphrase your textbook. Astrology is more "fun" than anything else and anyone who puts any stock in horoscopes (or horrorscopes !!!) is only fooling themselves. Your textbook has a few good pages on this topic in Chapter 2. Asking a question, "Does it make sense?" is always a good approach — is it consistent with observations and knowledge? For example, the statement that Derek Jeter (baseball player) had a batting average of 0.666 appears to be an unreasonable assertion — over what period of time — last season, last month, last week, yesterday? The Cosmological Principle Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

At the heart of modern astronomy is something called the Cosmological Principle . This principle is based on two fundamental tenets.  There is nothing special or unique about Earth — the Earth is not at the centre of the Universe or even our own solar system (of course, we now know that) — our location in the Universe is where it is by chance, nothing more, nothing less — nor is our galaxy anything special or different; there are thousands of galaxies like ours and unlike ours  The second is that the laws of physics and chemistry that describe what happens on Earth are valid throughout the Universe — in a sense, this follows from the first tenet — we are nothing special (astronomically speaking) Mankind did not always believe this. Again, not to bore you but to make the point once again, until Copernicus, Galileo and others, humans thought the Earth was at the centre of everything; that this was a special place; and that everything else, everything else , revolved around Earth. Further, we reasoned that the heavens were made of a different type of substance than Earth-bound objects, and that they had their own set of rules (e.g., Aristotle's belief that the natural state for any object was "at rest", except for the planets and stars for which their natural state was to move in perfect circles around Earth). However, science being what it is, and the scientific method being put to good use, "proved" that both of these strongly and firmly held ideas were wrong. Notice here that we are "proving" something wrong, not proving something right!!! Isaac Newton, Gravity and Orbits The Copernican Revolution resolved the problem of the place of Earth within the solar system, but the problem of planetary motion was only partly solved by Kepler’s laws. For the last 10 years of his life, Galileo studied the nature of motion, especially the accelerated motion of falling bodies. Although he made some important progress, he was not able to relate his discoveries about motion to those of the heavens. That final step was taken by Isaac Newton. As mentioned before Galileo died in January 1642. Some 11 months later, on Christmas day 1642, Isaac Newton was born in the English village of Woolsthorpe. Newton was a quiet child from a farming family, but his work at school was so impressive that his uncle financed his education at Trinity College, where he studied mathematics and physics. In 1665, plague swept through England, and the colleges were closed. During 1665 and 1666, Newton spent his time back home in Woolsthorpe, thinking and studying. It was during these years that he made most of his scientific discoveries. Among other things, he studied optics, developed three laws of motion, probed the nature of gravity, and invented calculus. The publication of his work in his book Principia in 1687 placed the fields of physics and astronomy on a new firm base. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

It is beyond the scope of these notes to analyze all of Newton’s work, but his laws of motion and gravity had an important impact on the future of astronomy. In order to understand his work, we must begin with a general framework for describing the motion of any object. Position and time specify where and when an object is. Speed is the rate at which an object moves (changes position). It is the total distance moved divided by the total time taken to move that distance. For example if it took you 2 hours to travel 100 km then your speed was 50 km/hour. Although we are used to thinking of speeds in km/hour, in science, the Standard International (SI) units are metres/second. Velocity specifies both speed and direction of travel of an object. For example if car A moves 60 km east in 2 hours and car B moves 60 km south in 2 hours, they have the same speed of 30km/hour, but their velocities are different because they are traveling in different directions. Thus, velocity can change if: (i) The speed changes (ii) The direction changes (iii) Both speed and direction change. Acceleration is the rate of change of velocity with time. It is thus the change in velocity divided by the time taken for the change to occur. Since velocity changes if speed changes, speeding up is an example of acceleration and slowing down is negative acceleration (in a direction opposing the direction of travel), or deceleration. On the other hand, velocity also changes if there is a change of direction; so turning is also an example of acceleration. Thus, an object can be traveling in a circle, let’s say, at constant speed but its direction is constantly changing and this translates into a change in velocity. Newton realized that the motion of all objects is a result of the forces (pulls or pushes) acting on them. He was able to find three universal laws of motion that made it possible to predict exactly how a body would move if all the forces acting on it were known. Newton’s first law of motion states that an object remains at rest or at constant velocity unless a net force acts to change its speed or direction. Thus when your car is at rest or traveling at a constant speed and direction, then the forces exerted by the wheels to drive you forward is balanced by the wind resistance and other forces in such a way that the net (total) force is zero. If you wanted to speed up, or slow down or change direction, then the engine would have to cause an additional force. The effect of this additional force is described by Newton’s second law . If the mass (amount of matter) of the object does not change, then the acceleration is proportional to the force exerted. Hence if you want to double your acceleration the applied force must be doubled. An example of acceleration that we are all familiar with is the acceleration due to gravity. All falling objects on Earth have a constant acceleration downwards towards the centre of the Earth. This acceleration was first pointed out by Galileo. The acceleration of gravity, g, is 9.8 metres per second per second, more commonly written as 9.8 m/s 2 . This means that if you drop any object, say an apple, from rest, its speed will increase by roughly 10 m/s with each second of falling, if one ignores air resistance. Thus after the first second its speed will be roughly 10 m/s, after two seconds its speed will be 20 m/s and so on until it crashes into the ground. Conversely, if you throw the apple into the air, there is still a constant acceleration of 9.8 m/s 2 downwards. Hence the speed of the apple will decrease by roughly 10 m/s every second until it comes to a standstill, at which point it will start falling back towards the ground with its speed increasing by 10 m/s every second. If you were to find yourself on the surface of Jupiter where the acceleration due to Jupiter’s gravity is 25.4 m/sec 2 then, of course, you (or any other object) would find your speed increasing by about 25 m/sec with each second of falling and in practically no time your speed would be quite high. In actual fact this wouldn’t happen on Jupiter because, as you will learn in Module Four, the surface of Jupiter consists of thick gases so the force due to air resistance would be considerable and you would soon reach some terminal velocity (speed) where the force Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

of gravity would be exactly balanced by the air resistance force. This is really more than you need to know but I’ve mentioned it because it’s interesting and it’s important to know that what you experience here on Earth will be quite different on any other body in the solar system. This brings us to Newton’s third law of motion stating that for every action (force) there is an equal and opposite reaction (force), although the action and reaction forces act on different bodies. This seems like such a simple law but one that most students have the most difficulty with, mainly because they forget about the second part of the law about “acting on different bodies”. In terms of the Earth-Moon system this means that the Earth’s gravity pulls on the Moon and that’s what keeps the Moon in orbit around the Earth. However, at the same time the Moon is pulling on the Earth and these two forces have exactly the same values although, as you can easily comprehend, they do act on different bodies, one on the Moon and the other one on the Earth. This law has great value to, let’s say, a spacecraft heading from Earth to Mars. As it moves along through space at constant speed (because the rockets are turned off) it moves in a straight line and at constant speed. Let’s suppose we turn on the rockets; this amounts to throwing hot gases away from the spacecraft in the opposite direction of motion. The action is that the spacecraft accelerates increasing its speed toward Mars. The reaction is that we’ve expelled some hot gases away from the spacecraft back toward Earth – action/reaction. So, Newton’s Laws of Motion are used all the time in astronomy whether it’s determining orbital mechanics (a fancy way of talking about measuring and determining the speeds of objects in motion around other objects) or working out how to get a spacecraft from Earth to Mars (or any other planet or moon) in the shortest possible time. Here’s a brief (4:24 min) YouTube video summarizing the ideas I’ve presented about Newton’s Laws of Motion. I hope it helps you to better understand them. The Universal Theory of Gravitation When Newton thought carefully about motion, he realized that some force must pull the Moon toward Earth’s centre. If there were no such force altering the Moon’s motion, then according to Newton’s first law, it would continue moving in a straight line and leave Earth forever. It can circle Earth only if Earth attracts it. Newton’s insight was to recognize that the force that holds the Moon in its orbit is the same force of gravity that makes apples and all other objects fall to the ground on Earth. Newtonian gravitation is sometimes called universal mutual gravitation. Newton’s third law points out that forces occur in pairs. If one body attracts another, the second body must also attract the first. Thus, gravitation is mutual. Furthermore, gravity is universal. That is, all objects with mass attract all other masses in the universe. The mass of an object is a measure of the amount of matter or ‘stuff’ in the object, usually expressed in kilograms. You may be used to thinking of ‘massive’ objects as very large objects. However, in science massive objects are those that contain a lot of matter. They may or may not be large. For example, a one-inch ball of lead is more massive than a large balloon full of air. In everyday life, the terms mass and weight are used interchangeably. Thus when you report your weight at the doctor’s office as 60kg you are actually reporting your mass. In science, mass is not the same as weight . Mass is an intrinsic property of an object and is the same no matter what forces are acting on an object. An object’s weight is the force that gravity Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

exerts on the object. Thus an object in space very far from Earth might have no weight, but it would contain the same amount of matter and would thus have the same mass that it has on Earth. Often, objects (even humans on board the International Space Station) are referred to as being in a “weightless” environment. You see objects floating inside the space station and it is assumed that they are now “weightless”. Quite frankly, this is all wrong. The ISS (and crew) orbit the Earth at about 420 km above Earth’s surface. At that height there certainly is a substantial gravitational field due to Earth’s presence so no thing associated with the ISS is weightless. Remember that weight is the force acting on an object due to the presence of Earth. It is because of this force and the tangential velocity of the ISS that it is able to be in orbit around the Earth. So, the point is that the ISS (and its crew) is constantly falling toward Earth (just like the Moon) – it just keeps missing! As long as it maintains its tangential velocity it will keep “missing” and remain in the same orbit around Earth. So, the astronauts, and everything associated with the ISS, are NOT weightless. To summarize, Newton’s universal law of gravitation states that the force of gravity attracting two objects to each other equals a constant times the product of their masses divided by the square of the distance between the objects. Gravity is universal: Your mass affects the planet Neptune and the galaxy M31, and every other object in the universe, and their masses affect you—although not much, because they are so far away and your mass is relatively very small. Orbital Motion Newton’s laws of motion and gravitation make it possible for you to understand why and how the moon orbits Earth, the planets orbit the Sun, and to discover why Kepler’s laws work. To understand how an object can orbit another object, you need to see orbital motion as Newton did. Begin by studying ‘Orbiting Earth’ on pages 66-67 (First Canadian Edition) and notice three important ideas: 1. An object orbiting Earth, and any orbiting object, is actually falling (being accelerated due to the gravitational force) toward Earth’s center. An object in a stable orbit continuously misses Earth because of its horizontal velocity. 2. Objects orbiting each other actually revolve around their mutual center of mass. 3. Notice the difference between closed orbits and open orbits. If you want to leave Earth never to return, you must give your spaceship a high enough velocity so it will follow an open orbit. When the captain of a spaceship says to the pilot, “Put us into a circular orbit,” the ship’s computers must quickly calculate the velocity needed to achieve a circular orbit. That circular velocity depends only on the mass of the planet and the distance from the center of the planet. Once the engines fire and the ship reaches circular velocity, the engines can shut down. The ship is in orbit and will fall around the planet forever, as long as it is above the atmosphere’s friction. No further effort is needed to maintain orbit, thanks to the laws Newton discovered. Newton’s laws of motion and his universal theory of gravitation enabled him to explain Kepler’s laws of planetary motion. Kepler’s first law that the planets move in elliptical orbits Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

is a direct result of the inverse square law of gravitation. Newton proved that any object moving in a closed orbit according to the inverse square law must follow an elliptical path. Furthermore, just like the spaceship in stable orbit around the Earth, the planets, the Moon and all objects in the universe will remain on their respective paths forever unless an external force (such as for example a collision with another object) acts on them. Newton’s inverse square law of gravitation also explains Kepler’s second law that reminds us that planets move faster when they are closer to the Sun. As the planets continuously fall towards the Sun in their orbits, they go faster when they approach the Sun, thanks to the inverse relationship between force and distance. A measure of a planet’s rotational motion is its angular momentum, which is proportional to its velocity and its distance from the Sun. As a result of Newton’s laws, in the absence of additional rotational forces the total angular momentum of a planet is conserved. Thus, when its distance from the Sun increases, its velocity must decrease to balance out the increased distance and vice versa. You can observe the conservation of angular momentum for yourself by watching an ice skater spinning on the ice. She can increase or decrease her velocity of rotation by pulling her arms in or spreading them out and thus increasing or decreasing her ‘distance’ from her Creative commons licence attribution: PhET Interactive Simulations, University of Colorado http://phet.colorado.edu . (To get this to work you will have to download the simulation by double-clicking on the picture. You may have to change your security settings (temporarily) to allow your computer to download the simulation and you may also have to upgrade your Java version. I know this should be simpler but right now that's how it is.) Newton was also able to combine his laws of motion with the law of gravitation to derive a relationship between a planet’s orbital period and average distance from the Sun, which was identical to Kepler’s third law, as detailed above. You now understand the power of Newton’s work. He was able to explain all the patterns of planetary motion observed by Kepler by using very simple and universal rules. But this was not all. Gravity is also the key to understanding another critical phenomenon on Earth: ocean tides. Newton's Universe Newton’s insights gave the world a new conception of nature. His laws of motion were general laws that described the motions of all bodies under the action of external forces. Just imagine! A few simple laws that can explain how your car accelerates, how the Canadian ice hockey team manoeuvres on ice, and even how the planets move! And furthermore, Newton’s laws and the theory of gravitation allow us to break the bonds of Earth and the Solar System and understand the motion of all objects in the universe. As you will see in later chapters, we can detect planets around other stars by observing the motion of the star as it gravitationally interacts with any planets orbiting it. We can calculate the mass of these new planets using the law of gravitation. Indeed this has been used to calculate the mass of Earth and all the other planets, and the Sun. We can even detect black holes at the centre of galaxies by observing the motion of objects around it. The story of the development of astronomy that you have just read is also the story of the development of the scientific method. Ancient astronomers began the process by carefully gathering and recording data. Gradually models were developed that best fit the data and Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

over time they were tested against observations and discarded if necessary. Good scientific theories are those that can make a broad range of predictions that can be confirmed against observations, and that can provide new insight into nature. Here we can hearken back to our study of Johannes Kepler and the development of his three laws of orbital motion. Recall that he took Brahe’s data and used it to realize that planets orbited the Sun in ellipses and not in circles. Science and astronomy progress today through the careful application of this method of studying nature. As the Nobel Prize winning physicist William Lawrence Bragg said, “The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them.” Sometimes this requires a huge leap of imagination and a questioning of our most strongly held beliefs. Indeed the shift from the geocentric to the heliocentric viewpoint was a harsh lesson in humility for humanity. Earth became merely another planet orbiting the Sun. But this first revolution of thought started us on a fantastic journey of scientific discovery. The efforts of Newton and his predecessors, all the way back to our ancient ancestors, opened the door to our modern way of scientific thinking and our understanding of the universe. The Physics of Heat The physics of heat, otherwise known as Thermodynamics, is a well-developed field of study within physics. It is also an important aspect of the study of astronomy. Therefore, we present in this section some of the more salient features of the concept of temperature, and those aspects of thermodynamics that will be relevant to our investigations. So, hang onto your hats; there'll be a hot time in the old town tonight, and won't that be cool!! We measure how hot (or cold) an object is by "taking its temperature". When we do this we use a temperature scale. In Canada, we now use the metric system of measurement resulting in temperature being measured in Centigrade or Celsius degrees. Not that long ago (and still in the United States) temperature was measured in Fahrenheit degrees. Evidently, there are two systems in use today in North America that measure temperature. Well, actually there are three systems as scientists often use a scale in degrees Kelvin. In the Fahrenheit system water freezes at 32° and boils at 212° and room temperature is around 68°; there doesn't seem to be any rhyme or reason to this system, although it has been in use for many years. In the Celsius system water freezes at 0° and boils at 100°. This seems a little more sensible. Room temperature is around 20°. The Kelvin temperature scale is the same as the Celsius scale except that the freezing point of water is shifted to 273.15 K (the ° sign is not used when writing temperatures in Kelvin) to result in the lowest possible temperature being 0 K. This temperature, 0 K, is often called absolute zero and is the temperature achieved when all atoms making up a sample are in their ground state. Absolute zero can never be achieved in the laboratory (what would you hold it in?) although scientists have got awfully close to it. So, when we discuss the planets in greater detail we will refer to their surface temperatures in Kelvin. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Thermal Energy If we examine an object at an atomic level (say a bottle of helium) we see that the individual helium atoms are moving around inside the bottle in all directions in a seemingly random way. Some are moving slowly while others are moving faster; some may even be momentarily at rest. The average kinetic energy (energy of motion) of the atoms is what we call temperature , so when we "take its temperature" we are really measuring the average kinetic energy of the atoms that make up the mass. This total kinetic energy of all particles in a system is often referred to as thermal energy . Typical speeds of atoms and molecules in the air around you actually move at quite high speeds — around 0.5 km/sec! What about a solid object? In such an object (a table, the floor, an apple) the individual atoms do not move around as freely as they do in a gas. The interatomic forces are strong enough to hold the atoms together in an array that is typical of that particular solid. However, the atoms vibrate back and forth in various directions in situ (at their location in the solid) and the speed and amplitude of vibration is an indication of the object's temperature. Heat Transfer Heat is transferred from one body to another body by three unique mechanisms:  conduction  convection  radiation Conduction Conduction occurs when the atoms in one part of the substance vibrate or oscillate faster, or in the case of a gas move around faster, (meaning a higher temperature) than at another part of the substance (meaning a lower temperature) — this vibrational /translational energy gets transferred along the chain of neighbours from the hot area to the cool area. Thus, heat energy (really energy of motion) is transferred from one part of the object to another in an attempt to make all parts of the object equal energy-wise, a spreading out or sharing of the thermal energy through diffusion. Some substances are better at this than others — metals are generally good conductors of heat (and also good electrical conductors) or good thermal conductors while non-metals (also called insulators) are generally poor thermal conductors, mainly because of the atomic structure of the materials. Convection While the best conductors of heat are generally solids (liquids less so, and gases very poorly), liquids and gases distribute heat by another process called convection. Here heat transfer is by the actual transfer of mass (unlike conduction where one atom/molecule jostles the one next to it and so on). A good example of this is what you experience at the beach. During the day the ground (beach) heats up more than the water and the air above the land also gets hotter. It's no secret that hot air rises (it's less dense and hence lighter) and to fill in the space cooler air Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

moves in from the air over the water. Cooler air then drops in over the water and a convection cycle is established. At night the opposite occurs with the convection cycle creating a wind away from the land. Convection also occurs during the heating of a pot of water on the stove — you might have noticed this while watching (waiting for?) a pot of water or soup to boil. Here, the bottom of the pot gets hot (conduction at work as the bottom of the pot is in contact with the hot stove element) warming the water in contact with the bottom of the pot. Warm water is less dense than cold water so the warm water rises being replaced by cooler water from above and a convection cell is established. Convection is one of the ways that terrestrial planets and moons cool down (like Earth, Mars, and Titan). Heat from the hot core of the planet heats up the portion of the mantle that it is in touch with core; this rocky material moves (slowly) to the outer part of the planet (similar to our warming pot of water) being replaced by cooler material from the upper portion of the mantle and a convection cell is established; see next below. Radiation The last form of heat transfer is very different from conduction and convection in that it actually makes use of a different form of energy to remove (or transport) heat from an object (or from one place to another). Inside a solid object light is emitted by atoms all the time. These photons are quickly absorbed by neighbouring atoms or molecules which themselves emit photons and the process continues within the object. So, within any object photons of various frequencies (hence energies) are bouncing around randomly. The average photon energy depends on the object's temperature. Eventually some of these photons make their way to the object's surface and are radiated away from the object, taking with it energy, thus cooling the object. The heat transferred through light (electromagnetic) waves is commonly called radiant energy or thermal radiation. The really interesting thing about this is that all objects do this — stars, cars, bars, Mars, even you! When an object cools by emitting light the radiation is not at one specific frequency (colour) but rather a spectrum (range) of frequencies (see below) depending on the temperature of the object. Two simple rules describe how a thermal radiation spectrum depends on the temperature of the emitting object:  Rule 1 — Hotter objects emit more total radiation per unit surface area (actually the radiated energy is proportional to the fourth power of the temperature (in K) — you don't need to know this — it's just interesting "stuff" — thus, a 600 K object radiates 16 times as much energy as a 300 K (room temperature) object)  Rule 2 — Hotter objects emit photons with a higher average energy (a fireplace poker which is relatively cool emits infrared radiation (not visible to us) but as it heats up it gets red (emitting higher energy photons) and at still hotter temperatures it might get white hot (emitting yellow and blue photons along with the red) Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

The graph shown below shows the intensity of light emitted (or energy per unit time) as a function of wavelength for several objects of different temperatures. You can see the validity of Rule 1 because the 15,000 K star clearly emits more total radiation than your 310 K human. Furthermore, the hot star emits the most photons at a shorter wavelength (higher energy) than our human who emits radiation primarily in the infrared (which is why tracking binoculars used by police at night allow observers to "see" humans). A relatively cool star (3000 K) emits mostly red light (such as Orion's Betelgeuse). Our Sun (5800 K) emits about the same amount of light of all visible colours so it looks yellow. A very hot star (Orion's Rigel) emits more blue light than any other visible colour so it appears bluish. This graph shows the amount of energy radiated by a body across the spectrum for a few objects at different temperatures. Types of Electromagnetic Radiation and their Sources Type of Radiation Wavelength Range (nm) Object Temperature Typical Sources Gamma Rays Less than 0.01 More than 108 K Nuclear reactions X-rays 0.01 - 20 106 – 108 K Supernova remnants and solar corona Ultraviolet 20 - 400 104 – 106 K Very hot stars Visible 400 - 700 103 – 104 K Stars Infrared 1000 - 1,000,000 10 – 103 K Cool clouds of dust, planets, satellites Radio More than 1,000,000 Less than 10 K No astronomical objects Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

are this cold Light - The Cosmic Messenger Light is obviously a very important part of astronomy. Let's face it; light is an important part of living! Ancient astronomers started to put together models of the universe by observing light from the Sun, light from the Moon, light from the planets, and light from the stars. Today we analyze light from stars to learn about the star's temperature, chemical composition, and motion. Light received from distant galaxies tells us about the expansion of the universe and possibly about the future of the universe. Light (radio signals) from spacecraft carries important information about properties of planets and their moons. Clearly, and this is a very important point, everything we know about our solar system (with the exception of what we have learned from manned or robotic lander missions), everything we know about our own galaxy and everything we know about the universe, we know because of the light we have observed and analyzed originating from beyond our planet Earth. Light is not just our primary tool; it’s pretty much our only tool. Thus, it is imperative that we understand what light is, what its properties are, and how we use it to explore the universe around us. What is Light? From a scientific perspective light is a transverse, electromagnetic wave propagating through space. Now that we've got that out of the way, let's find an easier way to describe light. Actually, light is quite analogous to water waves. By observing water waves you learn that they move away across the surface of the water from the source of the wave (a bobbing boat, the spot where a thrown stone enters the water, the location where a raindrop meets the puddle). Closer examination reveals that although the wave moves across the surface of the water, the water itself doesn't actually move in the direction of the wave. Observe a leaf floating on the water; as the wave "goes by" the leaf actually moves up and down perpendicular to the direction of the wave. This indicates that the water just under the leaf must also simply move up and down. Light has the same characteristics. As the light moves along through space, the coupled electric and magnetic fields vary in a wave-like fashion in directions perpendicular to the light ray's direction. It is not essential that you understand this aspect of light. Normally we think about light as only the visible (to the human eye) part of the entire light spectrum. In actual fact, the visible portion of the light spectrum is a very small part of the entire range of light. From the picture below you can see that X-rays, gamma rays, Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

ultraviolet, infrared, and radio and television waves are also light. The only thing that differs in all of these is the frequency of the wave. What is Light? From a scientific perspective light is a transverse, electromagnetic wave propagating through space. Now that we've got that out of the way, let's find an easier way to describe light. Actually, light is quite analogous to water waves. By observing water waves you learn that they move away across the surface of the water from the source of the wave (a bobbing boat, the spot where a thrown stone enters the water, the location where a raindrop meets the puddle). Closer examination reveals that although the wave moves across the surface of the water, the water itself doesn't actually move in the direction of the wave. Observe a leaf floating on the water; as the wave "goes by" the leaf actually moves up and down perpendicular to the direction of the wave. This indicates that the water just under the leaf must also simply move up and down. Light has the same characteristics. As the light moves along through space, the coupled electric and magnetic fields vary in a wave-like fashion in directions perpendicular to the light ray's direction. It is not essential that you understand this aspect of light. Normally we think about light as only the visible (to the human eye) part of the entire light spectrum. In actual fact, the visible portion of the light spectrum is a very small part of the entire range of light. From the picture below you can see that X-rays, gamma rays, ultraviolet, infrared, and radio and television waves are also light. The only thing that differs in all of these is the frequency of the wave. Light and Matter Light on its own is fairly interesting but is much more impressive when it interacts with matter. Every time light interacts with some object, one or more of the following happens — absorption, transmission, or reflection. If you paint your bedroom walls green, dyes in the paint absorb all visible light frequencies except green, which get reflected, giving your walls a green colour. An orange basketball absorbs all "colours" except those that combine to give the ball an "orange" colour. The source of all light is atomic or molecular. Light comes from an atom when it undergoes a transition from one energy level to a lower one. The frequency of the light is directly dependent on the difference between the energy levels. The higher the energy difference the closer the light is to the blue end (and beyond) of the spectrum. Because there are many different energy levels possible in an individual atom there are a number of different light frequencies that can be generated by a single atom. Each element (H, He, Na, Au, etc.) has a spectrum (a series of lines) that is unique — a fingerprint Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

characteristic of that particular element. Such a spectrum is called an emission spectrum, as shown in the picture here that is a spectrum for hydrogen. Much of this is outlined on a two- page spread in your textbook in Section 5.5 – please look at these pages carefully. Doppler Shift An interesting and useful phenomenon concerning light (and sound) waves called the Doppler Effect was first correctly explained by Christian Doppler in 1842. Note that this phenomenon is known as the Doppler Effect and not the Doppler Affect (a common error). If a sound source is moving toward an observer the waves in front of the sound source get bunched up (closer together) so that the observer hears more waves per second than if the sound source was not moving. Similarly, if the sound source is moving away from the observer the waves behind the sound source get pulled apart so that the observer hears fewer waves per second than if the sound source was not moving. This situation is shown below where the sound source is a fire truck. Perhaps you have experienced this situation waiting at a sidewalk and hearing the pitch of an emergency vehicle siren or bell drop as it passes. Telescopes - Types, Properties and Uses Before we get to the point of learning about the different types of telescopes and how they work we will study a little about common optical devices. In actual fact both the eye and the camera, optical devices we will study first, are adjuncts to the telescope. Obviously we use our eyes to "see" the images produced by telescopes and we use cameras to record those images. Thus, learning about the optics of the eye and the camera first seems a logical approach. By now you will have realized that we have learned, or will learn, a great deal about optics, an important branch of physics. See how sneaky we physicists are; we teach physics through astronomy!! Common Properties of Optical Devices All optical devices use light from some part of the electromagnetic spectrum (often the visible part). All optical devices normally gather parallel light rays and make use of a focussing device of some sort. All have some kind of a light detection device which transforms the light information into a more usable form (electric, chemical, etc.). As well all optical devices have some way of controlling the intensity of the light. Human Eye Our study of optical devices starts with the most common (but complex) light-sensitive instrument — the human eye. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

The eye has a pupil (iris), a lens (for focusing) and a retina (for detecting the light). Ideally light focuses on the retina which is really a focal plane (somewhat of a misnomer because it is actually a curved surface). One important feature of this optical system is the fact that the image is inverted, as shown above. Thus, you constantly see things upside down but learn early in life to flip the image top to bottom. All optical instruments operate this way so when you first use a telescope you must learn to adjust your thinking to seeing star fields upside down and backwards unless you employ an inverting device. Remarkably your pupil dilates in low light environments to allow more light in, allowing you to see better in the dark. Angular Resolution Angular Resolution is a measure of the ability to separate two closely-spaced lights. The human eye has an angular resolution of about 1 arc minute (1/60th of a degree). So, if you see a star in the night sky, are you really seeing one star or two (most stars are at least binary star systems)? With the naked eye you will see two distinct stars if they are separated by 1 arc minute or more. Angular resolution is an important aspect of all optical devices. Cameras Cameras have optics similar to the eye with a lens (often interchangeable to change the focal length), an aperture (to change the amount of light which enters the camera), and a film (to record the image). Another part, called the shutter (similar to our eyelid), allows light to be exposed to the film for a controlled amount of time. Charge-coupled Devices (CCDs) The quantum efficiency (% of photons striking the surface detected) of the three main optical recording devices are as follows:  human eye — 1%  photo film — 10%  CCDs — 90%. Today, digital devices and camcorders employ an image recording device known as a charge-coupled device or CCD. A CCD is a silicon chip made of grid of picture elements Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

(pixels) which are very sensitive to light and convert photon energy into an electronic charge which accumulates. The overall image is stored in a computer for later processing. Telescopes Telescopes have come a long way from the modest tool that Galileo first used to examine the heavens. Today there are large, land-based, visible-light telescopes (the largest will be a 10.4 metre diameter located in the Canary Islands); X-ray observatories; ultraviolet spectroscopic units; Very Large Array radio wave telescopes; and the Hubble Space Telescope — an Earth-orbiting, visible-light telescope that has brought us amazing pictures of our own solar system and deep-space objects. There are two basic types of visible-light telescopes; refractive and reflective. Refractive Telescopes The basic design of refractive telescope is much like human eye in that it takes light in through a lens, the image of which is viewed with an eyepiece (a common part of all telescopes). The largest refractive telescope is 1 metre in diameter with a telescopic tube 19.5 metres long. There are several problems with refractors — their large size and weight and the difficulty in maintaining a consistent glass composition and surfacing during the manufacturing process. Also, something called chromatic aberration (different light colours focus at different spots) result in fuzzy images. The telescope model on the left (below) is an example of a refracting telescope. Reflecting Telescope Reflecting telescopes are much more common, having none of the difficulties discussed for refractors. Reflectors use one optical surface to collect light — a spherical mirror surface — which focuses the light at a point in front of the mirror. The telescope on the right (above) is an example of a reflecting telescope. Various arrangements are used to view the image. A Cassegrain focus, a Newtonian focus and a Schmidt-Cassegrain focus are shown below. Properties of Telescopes The two most fundamental properties of any telescope are its light-gathering power and its resolving power. Note that magnification is NOT listed as an important factor. Light-gathering power — Telescopes are described by the diameter of the primary mirror (or lens) — a 6" reflector has a diameter of 6" and a light-collecting area of about 28 in 2 . The largest optical telescope today actually the Gran Telescopio Canarias in La Palma, Canary Islands at 10.4 m followed closely by the Keck I (or Keck II) on Mauna Kea in Hawaii Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

(10.0 m). These telescopes consist of 36 hexagonal mirrors pieced together to form a very large light-collecting device. Resolving power or Angular Resolution — Angular resolution is the ability to resolve two closely spaced light sources. The angular resolution is generally greater the larger the telescope. Perfect angular resolution is limited by the very wave nature of light which causes interference patterns resulting in blurred images. The angular resolution limit owing to this phenomenon is called its diffraction limit , and is not likely a term that you will ever use unless you are buying a high-end telescope (if you do I hope you will let me come and have a peek through it!!). Telescope Uses Naturally, telescopes are used in obtaining pictures of bodies in the sky (planets, Sun, moons, individual stars, binary stars, star clusters, galaxies, planetary systems, etc.). They are also used in carrying out spectroscopy — the science of analyzing light to learn of its constituent parts thereby determining the composition of the body being examined. As well, telescopes are involved in longitudinal studies — measuring how light from objects varies with time. None of these uses are limited to any particular part of the spectrum as telescopes have been built for light of all kinds — visible, infrared, ultraviolet, X-ray, microwave, γ-rays, radio (long, medium, short), discussed later. Visible light ground-based telescopes (the ones most of us use) must contend with light pollution and weather conditions. Anyone who has tried to view the sky, even with the naked eye, knows well these difficulties. The picture below demonstrates well the growing problem of Earth-based light pollution. To circumvent this difficulty some telescopes have been placed in orbit about the Earth, above the atmosphere. The most famous of these is the Hubble Space Telescope (HST), commonly known just as the Hubble. The Hubble operates mostly in the visible part of the spectrum. Others operate at different frequencies. The Spitzer Space Telescope operates in the infrared. The James Webb Space Telescope (not yet in orbit) is proposed to replace the Hubble and will operate in the near-infrared. The Chandra X-ray Observatory obviously operates in the X-ray region of the spectrum. Observing objects at across the entire spectrum provides us with much more information than viewing at only visible wavelengths. Some of the most spectacular telescopes are actually arrays of radio telescopes which make use of radio interferometry, possible because light (of all frequencies) is a wave phenomenon. The Very Large Array (VLA), shown here, consists of 27 telescopes that can be moved along train tracks which form a Y shape — the result is a system equivalent to a single huge (130 metre) telescope. Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

Most of everything we know from outside Earth we know because of our use of what? -Light Light is a wave phenomenon with which of the following characteristics? - Wavelength, Frequency, Energy, Speed What is the range of the wavelength of visible light? - 400- 700 nanometers From highest frequency to lowest frequency what is the correct sequence? - Gamma, Xray, Ultraviolet, Visable, infrared, radio waves The Doppler Efect is a way to determine what? - Velocity of an object moving away from us The two basic types of telescopes are what? - Reflective and refractive The larger the size of the telescope the greater the what? - Light gathering ability The main problem that ground-based telescopes have to contend with is - The earths atmosphere, marrying atmospheric conditons, light polluton Which of the following statements about the Hubble Space Telescope is false? - it was designed by a famous astronomer named Edwin Hubble What is the main advantage of the Hubble Space Telescope? - It orbits above the earths atmosphere The Teutonic name Thor is related to the heavenly body and English name: Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

- Thursday, Jupiter Stonehenge was built by whom? - No body knows for sure The date for Easter is determined by - Full moon following spring equinox Early Greek philosophers who infuenced the development of scientifc thought included - Aristotle, Socrates, Plato, Ptolemy Nicolaus Copernicus was important because - although he didn’t come up with the concept of the heliocentric model he was convinced that it was the correct model and wrote about it in a published book Galileo was a very important fgure in the development of astronomy. Which of the following statements about Galileo’s accomplishments is false? - Galileo looked at the moon through his telescope and observed rivers, mountains and lakes filled with liquid Galileo was a very important fgure in the development of astronomy. Which of the following statements about Galileo’s accomplishments is false? - The force of gravity is inversely proportional to the square of the distance between a planet and the sun - The scientifc method involves observing some phenomenon, hypothesizing a theory, observing some more, refning the hypothesis, and so on - True If you run down the street covering 2 km in 30 minutes your speed is - 1.1 m/sec Acceleraton is - The rate of change of speed (or velocity) with time Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465

the acceleration due to gravity on the surface of the Earth is - 9.8 m/sec squared Newton’s Universal Law of Gravitation tells us that the force between two objects - Varies inversely as the square distance between the two objects Which of the following statements about energy is false? - Energy comes in little blobs that we have seen and can describe Which of the following statements about momentum is true? - Momentum is the product of mass and velocity An object is able to stay in orbit around another object because - It has just the right tangential speed Two diferent tempuratures scales are - Kelvin and Fahrenheit Heat is transferred from one body to another by - Conduction, radiation, convection A hot star emits primarily what colour of visible light? - Blue Downloaded by Sawaab .A (sawaabanas@hotmail.com) lOMoARcPSD|7715465