Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 2, Problem 6E
Explain the origin of the magnitude designation for determining the brightness of stars. Why does it seem to go backward, with smaller numbers indicating brighter stars?
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Review Conceptual Example 3 for information pertinent to this problem. When we look at a particular star, we are seeing it as it was 307 years ago. How far away from us (in meters) is the star? Take a year to be 365.25 days.
Question A1
Use a diagram to explain what is meant by the parallax angle, p, for a star observed twice from
Earth, with a 6-month interval between each observation. Hence define the parsec, and calculate
its value in astronomical units and metres. The star Betelgeuse is observed to have a parallax
angle p = 4.5 x 10-³ arcseconds. State the distance of Betelgeuse in units of parsecs and light
years.
Which of the following is least reasonable regarding the magnitude scale:
Group of answer choices
The numerical difference between a star's absolute and apparent magnitudes is a measure of the distance to the star.
If the Sun were moved to a distance of 10 parsecs, its apparent magnitude would be about 4.8 and it would therefore not be visible to the naked eye.
The fact that Sun's absolute magnitude of 4.8 is greater than the Sun's apparent magnitude of -27 implies that the Sun is a lot closer than 10 parsecs.
Apparent magnitude measures a star's apparent brightness when viewed at the star's actual distance from the observer.
A star's absolute magnitude is its apparent magnitude when viewed from a distance of 10 parsecs.
Chapter 2 Solutions
Astronomy
Ch. 2 - From where on Earth could you observe all of the...Ch. 2 - Give four ways to demonstrate that Earth is...Ch. 2 - Explain, according to both geocentric and...Ch. 2 - In what ways did the work of Copernicus and...Ch. 2 - What were four of Galileo’s discoveries that were...Ch. 2 - Explain the origin of the magnitude designation...Ch. 2 - Ursa Minor contains the pole star, Polaris, and...Ch. 2 - How many degrees does the Sun move per day...Ch. 2 - How many degrees does the Moon move per day...Ch. 2 - Explain how the zodiacal constellations are...
Ch. 2 - The Sun was once thought to be a planet. Explain...Ch. 2 - Is the ecliptic the same thing as the celestial...Ch. 2 - What is an asterism? Can you name an example?Ch. 2 - Why did Pythagoras believe that Earth should be...Ch. 2 - How did Aristotle deduce that the Sun is farther...Ch. 2 - What are two ways in which Aristotle deduced that...Ch. 2 - How did Hipparchus discover the wobble of Earth’s...Ch. 2 - Why did Ptolemy have to introduce multiple circles...Ch. 2 - Why did Copernicus want to develop a completely...Ch. 2 - What two factors made it difficult, at first, for...Ch. 2 - What phases would Venus show if the geocentric...Ch. 2 - Describe a practical way to determine in which...Ch. 2 - What is a constellation as astronomers define it...Ch. 2 - Draw a picture that explains why Venus goes...Ch. 2 - Show with a simple diagram how the lower parts of...Ch. 2 - Parallaxes of stars were not observed by ancient...Ch. 2 - Why do you think so many people still believe in...Ch. 2 - Consider three cosmological perspectives-the...Ch. 2 - The north celestial pole appears at an altitude...Ch. 2 - What were two arguments or lines of evidence in...Ch. 2 - Although the Copernican system was largely correct...Ch. 2 - During a retrograde loop of Mars, would you expect...Ch. 2 - The Great Pyramid of Giza was constructed nearly...Ch. 2 - Explain why more stars are circumpolar for...Ch. 2 - What is the altitude of the north celestial pole...Ch. 2 - If you were to drive to some city south of your...Ch. 2 - Hipparchus could have warned us that the dates...Ch. 2 - Explain three lines of evidence that argue against...Ch. 2 - What did Galileo discover about the planet Jupiter...Ch. 2 - What did Galileo discover about Venus that cast...Ch. 2 - Suppose Eratosthenes had found that, in...Ch. 2 - Suppose Eratosthenes’ results for Earth’s...Ch. 2 - Suppose you are on a strange planet and observe,...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- Describe two ways of determining the diameter of a star.arrow_forwardUrsa Minor contains the pole star, Polaris, and the asterism known as the Little Dipper. From most locations in the Northern Hemisphere, all of the stars in Ursa Minor are circumpolar. Does that mean these stars are also above the horizon during the day? Explain.arrow_forwardConsider two identical stars, A and B. Star B is 10 times farther away than star A. What is the difference in magnitudes between the two stars?arrow_forward
- On Earth, the parallax angle measured for the star Procyon is 0.29 arcseconds. If you were to measure Procyon's parallax angle from Venus, what would the parallax angle be? (Note: Earth's orbital radius is larger than Venus's orbital radius.) A. more than 0.29 arcseconds B. 0.29 arcseconds C. less than 0.29 arcseconds D.zero arcseconds (no parallax)arrow_forwardProblem 5. Imagine that you observe a star field twice, with a six-month gap between your observations, and that you see the two sets of stars shown below. Which do you think is closest to the observer? Figure 1: Schematic of image of stars A,B, and P taken six months apart. Problem 6. Suppose the angular separation between stars A and B is 0.5 arcseconds. How far would you estimate star P to lie from the observer?arrow_forward15: A star has a parallax angle of 0.0270 arcseconds and an apparent magnitude of 4.641. What is the distance to this star? Answer: 37 16: What is the absolute magnitude of this star? Answer:1.8 17: Is this star more or less luminous than the Sun? Answer "M" for More luminous or "L" for Less luminous. (HINT: the absolute magnitude of the Sun is 4.8) Answer: M 18: What is the luminosity of this star? (HINT: The luminosity of the Sun is 3.85×1026 W.) Please answer question #18, #15-17 are correct, the photos provide the work for them.arrow_forward
- please help with this astronomy physics questionarrow_forwardUse a diagram to explain what is meant by the parallax angle, p, for a star observed twice from Earth, with a 6-month interval between each observation. Hence define the parsec, and calculate its value in astronomical units and metres. The star Betelgeuse is observed to have a parallax angle p = 4.5 × 10−3 arcseconds. State the distance of Betelgeuse in units of parsecs and light years.arrow_forwardIf we view a star now, and then view it again 6 months later, our position will have changed by the diameter of the Earth's orbit around the sun. For nearby stars (within 100 light-years or so), the change in viewing location is sufficient to make the star appear to be in a slightly different location in the sky. Half of the angle from one location to the next is known as the parallax angle (see figure). Parallax can be used to measure the distance to the star. An approximate relationship is given by d = 3.26 p , where d is the distance in light-years, and p is the parallax measured in seconds of arc. Vega is a star that has a parallax angle of 0.13 second. How far is Vega from the sun? Note: Parallax is used not only to measure stellar distances. Our binocular vision actually provides the brain with a parallax angle that it uses to estimate distances to objects we see. (Round your answer to two decimal places.) light-yearsarrow_forward
- Star X has an apparent magnitude of 0.03 and an absolute magnitude of 0.6. If it were moved to be twice as close to Earth as it is now, which of the following would occur? A. apparent magnitude number would decrease O B. absolute magnitude number would increase C. absolute magnitude number would decrease O D. apparent magnitude number would stay the same E. apparent magnitude number would increasearrow_forwardThe nearest star to our sun is Proxima Centauri, at a distance of 4.3 light-years from the Sun. A light-year is the distance that light travels in one year (365 days). How far away, in kilometers, is Proxima Centauri from the Sun?Express your answer using two significant figures.arrow_forward1. Planet A has an orbital period of 12 years and radius that is 0.033 times the radius of the star. Calculate the fractional dip of the star brightness in the case that planet A is transiting. Give the answer as a number. Quote the formula you use and explain any assumptions you have to make. 2. Planet B has an orbital period of 1 year and is located closer to its star than planet A. You succeed in detecting planet B with the radial velocity technique as well! From this measurement you calculate a minimum mass of planet B to be 75% that of the Earth. (a) Since you detect the planet with both transit method and radial velocity method, what do you know about the inclination of the planetary system? (b) Given this inclination, estimate the true mass of planet B (in units of Earth mass). You do not need to do a detailed calculation, just explain the argument. 3. You also measure the radius of planet B to be the same as Earth, one Earth radius. (a) How does the density of planet B compare…arrow_forward
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