FinalReviewWorksheet-Fall2023

P a g e 1 | 6 ASTR1000 – F INAL R EVIEW W ORKSHEET Instructions. Print this worksheet and complete the following fill in the blank exercises using the keywords listed at the start of each section. There are more keywords than blanks; not all keywords must be used. If a word appears two or more times in the list, it can be used multiple times. After you complete all the sections, submit your answers electronically in the “Quizzes” tool of folio, quiz “Final Review”. You have only one attempt to submit your answers. T HE S KY Chapters 2 and 3 Isaac Newton Nicolaus Copernicus Galileo Galilei Aristotle Tycho Brahe Ptolemy Johannes Kepler prograde apparent motion rotation heliocentric geocentric geometric Sun constellation stellar cluster stellar group orbital retrograde galactic circle orbit epicycle circles ellipses parabolas deferent focus Earth galaxy Sun heavens Moon Earth ecliptic zenith rotation axes celestial sphere celestial poles nucleus stellar sphere The astronomical knowledge of ancient cultures is the foundation of modern astronomy, including the idea of dividing the sky into groups of stars, each of which is called a (1)_______________, which they imagined traced out pictures in the sky. Ancient astronomers believed that all stars were fixed on a sphere surrounding the Earth, called the (2)_______________. While this is not true, astronomers today find this model helpful in visualizing the (3)_______________ of celestial objects. Some points and lines on the celestial sphere are particularly useful; the point directly above the head of an observer is called the (4)_______________ , and the sky seems to turn about two points known as the (5)_______________ . The apparent path followed by the Sun around the celestial sphere is called the (6)_______________ . Ancient astronomers invented models of the universe to explain the apparent motions of visible objects in the heavens. Greek scholars believed the (7)_______________ is stationary and located at the center of the universe. A model of this kind is called a (8)_______________ model. Later, Greek astronomer (9)_______________ expanded this model with each planet moving in a small circle called an (10)_______________, whose center in turn moves following the rotation of a larger sphere called the deferent.

P a g e 2 | 6 Today we know the Sun only appears to rise and set each day. This is not due to an actual motion but rather due to Earth´s (11)_______________. Over the course of the year, the constellations visible in the night sky slowly change. This is due to the (12)_______________ motion of the (13)_______________ around the (14)_______________. It was until the sixteenth century that Polish astronomer (15)_______________ devised the first comprehensive (16)_______________ model, with all the planets moving on circular orbits around the (17)_______________. Johannes Kepler refined this model based on the astronomical observations of Danish astronomer (18)_______________, and developed a series of principles known as Kepler’s three laws, which describe the planetary orbits as (19)_______________, with the sun located at one (20)_______________.

P a g e 4 | 6 L IGHT FROM S TARS Chapters 17 and 18. color line color index temperature density luminosity luminosity apparent brightness mass green blue red B C K main sequence main stellar band largest brightest faintest Sirius Betelgeuse Kepler Hipparchus Hubble-Reynolds Hertzsprung–Russell spectral index absorption line The only source of information we have to determine the properties of stars is the light we receive from them. The total amount of energy a star emits per second is called its (1)_______________ , not to be confused with its (2) _______________, which is the amount of a star’s energy per unit area that reaches the Earth. Around 150 B.C.E., (3) _______________was the first astronomer to create a map of stars that included eye estimations of their brightness. He sorted the stars into six levels of brightness he called magnitudes. The (4) _______________ stars were referred as 1 st magnitude, and the (5) _______________ he could see were referred as 6 th magnitude stars. Modern measurements show that some stars Hipparchus classed within 1 st magnitude are actually brighter than what he estimated and, have been assigned negative magnitude values. (6) _______________ , the star with the highest apparent brightness has a magnitude of -1.5. Stars have different colors, which are indicators of their surface (7) _______________ . The hottest stars tend to appear (8) _______________ , whereas the coolest stars are (9) _______________ . A method to measure the color, and thus the temperature of stars, is to determine the difference in the star’s magnitudes at any two different colors or spectral regions. This is called a (10)_______________ of the star, for example the green minus the red magnitudes (g-r). Another method to estimate the temperature of a star is by analyzing its spectra. The (11)_______________ patterns in the spectra of a star are mainly a result of the star’s temperature, which is used to sort stars into seven spectral classes. Ordered from higher to lower temperature, the spectral classes are: O, (12) _______________ , A, F, G, (13) _______________ , and M. Later classes L, T and Y have been added to include objects discovered recently. The (14) _______________ diagram, or H–R diagram, is a plot of stellar (15) _______________ on the vertical axis against surface temperature on the horizontal axis. Most stars lie on the (16)_______________ , which a region that extends diagonally across the H–R diagram from high temperature and high luminosity to low temperature and low luminosity. Theoretical models show that the position of a star along the main sequence is determined by its initial (17)_______________. The hottest and more luminous stars have the (18) _______________ masses.

P a g e 5 | 6 S TELLAR E VOLUTION Chapters 16, 22 and 23 hydrogen helium carbon iron mass temperature radius proton-to-proton Betelgeuse Sirius The Sun Chandrasekhar limit Hubble constant red supergiants red giants contract more less brighter fainter shorter longer redder white dwarf planetary nebula neutron star supernova black hole planet Main-sequence stars derive their energy from the fusion of hydrogen into (1) _______________ . This conversion of chemical composition takes place through a set of reactions called the (2)_______________ chain, in which protons collide with other protons to form helium nuclei. Eventually, as stars age and most of the hydrogen in its nucleus is converted into helium, the rate of energy production drops and their core begins to (3) _______________ . The energy of the inward-falling material is converted to heat that increases the temperature of the shell of hydrogen nuclei just outside the core, becoming hot enough for hydrogen fusion to begin. New energy produced by fusion of this hydrogen now pours outward from this shell and begins to heat up layers of the star farther out, causing them to expand while the core continues to contract. The star gets larger, (4) _______________ , and (5) _______________ luminous as it expands and cools. The star therefore leaves the main-sequence band and moves upward ( (6)_______________ zone) and to the right (cooler surface temperature) on the H-R diagram. Over time, massive stars become (7) _______________ , and lower- mass stars like the Sun become (8)_______________ . (9) _______________star in the constellation of Orion, is a good example of a star nearing its death as a red supergiant. The lifetime of stars depends on its (10) _______________ . More massive stars complete each stage of evolution in a (11) _______________time than lower-mass stars. During the red giant/supergiant stages stellar pulsations, and violent events can drive atoms in the outer atmosphere away from the star and cause it to lose a substantial fraction of its mass into space. As a result, aging stars are surrounded by one or more expanding shells of gas known as (12) _______________ . Stars whose final mass just before their death is less than about 1.4 times the mass of the Sun collapse until gravity is balanced by degeneracy pressure from the electrons. This collapse is the final event in the life of the star and what remains becomes a (13) _______________ . The maximum mass that a star can end its life with and still become a white dwarf, 1.4 MSun, is called the (14) _______________ . Stars with end-of-life masses that exceed this limit have a different kind of end. In a massive star, the weight of the outer layers is sufficient to several other fusion reactions involving heavier elements, that comes to an end when the core accumulates (15)_______________ atoms. If the mass of a star’s core exceeds the Chandrasekhar limit (but is less than 3 MSun), the core collapses, forming a (16) _______________ . The core rebounds and transfers energy outward, blowing off the outer layers of the star in a (17) _______________ explosion.