The Cosmic Perspective (9th Edition)
9th Edition
ISBN: 9780134874364
Author: Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit
Publisher: PEARSON
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Chapter 21, Problem 51EAP
To determine
The mass of the supermassive black hole.
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Which statement concerning black hole masses and Schwarzschild radii is not true?
A. Even an object as small as you could become a black hole if there were some way to
compress you to a size smaller than your Schwarzschild radius.
B. The more massive the black hole, the larger the Schwarzschild radius.
C. For black holes produced in massive star supernovae, Schwarzschild radii are typically a
few to a few tens of kilometers.
D. In a binary system with a black hole, the Schwarzschild radius depends on the distance
from the black hole to the companion star.
The supermassive black hole at the center of a galaxy has a mass of 6.5 billion solar masses. If we assume that it is a Schwarzschild black hole, what is the radius of this black hole?
A. 18 light hours
B. 20 light hours
C. 16 light hours
D. 14 light hours
Is the answer A?
S. radius = 3 x 6.5 x 109 x 9.26567-10 = 18.1 light hours
Thanks!
An astronomer observed the motions of some galaxies. Based on his observations, he made the following statements. Which one of them is most likely to be false? Take Hubble's constant to be 67 km/s/Mpc.
A. A galaxy observed to be moving away from us at a speed of 70 km/s is at a distance of about 1 Mpc from us.
B. A galaxy observed to be moving away from us at a speed of 700 km/s is at a distance of about 10 Mpc from us.
C. A galaxy observed to be moving away from us at a speed of 7000 km/s is at a distance of about 100 Mpc from us.
D. A galaxy observed to be moving away from us at a speed of 70000 km/s is at a distance of about 1 Gpc from us.
Is the answer D? Thank you!
Chapter 21 Solutions
The Cosmic Perspective (9th Edition)
Ch. 21 - Prob. 1VSCCh. 21 - Prob. 2VSCCh. 21 - Prob. 3VSCCh. 21 - Prob. 4VSCCh. 21 - Prob. 1EAPCh. 21 - Prob. 2EAPCh. 21 - Prob. 3EAPCh. 21 - Prob. 4EAPCh. 21 - Prob. 5EAPCh. 21 - Prob. 6EAP
Ch. 21 - Prob. 7EAPCh. 21 - Prob. 9EAPCh. 21 - Prob. 10EAPCh. 21 - Prob. 11EAPCh. 21 - Prob. 12EAPCh. 21 - Prob. 13EAPCh. 21 - Prob. 14EAPCh. 21 - Prob. 15EAPCh. 21 - Prob. 16EAPCh. 21 - Prob. 17EAPCh. 21 - Prob. 18EAPCh. 21 - Prob. 19EAPCh. 21 - Prob. 20EAPCh. 21 - Prob. 21EAPCh. 21 - Prob. 22EAPCh. 21 - Prob. 23EAPCh. 21 - Prob. 24EAPCh. 21 - Prob. 25EAPCh. 21 - Prob. 26EAPCh. 21 - Prob. 27EAPCh. 21 - Prob. 28EAPCh. 21 - Prob. 29EAPCh. 21 - Prob. 30EAPCh. 21 - Prob. 31EAPCh. 21 - Prob. 32EAPCh. 21 - Prob. 34EAPCh. 21 - Prob. 36EAPCh. 21 - Life Story of a Spiral. Imagine that you are a...Ch. 21 - Prob. 39EAPCh. 21 - Prob. 40EAPCh. 21 - Prob. 41EAPCh. 21 - Prob. 42EAPCh. 21 - Prob. 43EAPCh. 21 - Prob. 44EAPCh. 21 - Prob. 45EAPCh. 21 - Prob. 46EAPCh. 21 - Prob. 47EAPCh. 21 - A Nearby Starburst. The galaxy M82, shown in...Ch. 21 - Prob. 49EAPCh. 21 - Prob. 50EAPCh. 21 - Prob. 51EAPCh. 21 - Prob. 52EAPCh. 21 - Prob. 53EAP
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- The best evidence for a black hole at the center of the Galaxy also comes from the application of Kepler’s third law. Suppose a star at a distance of 20 light-hours from the center of the Galaxy has an orbital speed of 6200 km/s. How much mass must be located inside its orbit?arrow_forwardThe first clue that the Galaxy contains a lot of dark matter was the observation that the orbital velocities of stars did not decreases with increasing distance from the center of the Galaxy. Construct a rotation curve for the solar system by using the orbital velocities of the planets, which can be found in Appendix F. How does this curve differ from the rotation curve for the Galaxy? What does it tell you about where most of the mass in the solar system is concentrated?arrow_forwardA stellar black hole may form when a massive star dies. The mass of the star collapses down to a single point. Imagine an astronaut orbiting a black hole having eight times the mass of the Sun. Assume the orbit is circular. a. Find the speed of the astronaut if his orbital radius is r = 1 AU. b. Find his speed if his orbital radius is r = 11.8 km. c. CHECK and THINK: Compare your answers to the speed of light in a vacuum. What would the astronauts orbital speed be if his orbital radius were smaller than 11.8 km?arrow_forward
- Observations indicate that each galaxy contains a supermassive black hole at its center. These black holes can be hundreds of thousands to billions of times more massive than the Sun. Astronomers estimate the size of such black holes using multiple methods. One method, using the orbits of stars around the black hole, is an application of Kepler's third law. The mass of the black hole can be found by using the given equation, where a is the semi-major axis in astronomical units, P is the period in years, and k is a constant with a value of 1 Mo X year²/ AU³. a³ M = k- p² What is the mass of a supermassive black hole if a star orbits it with a semimajor axis of 959 AU and a period of 13.3 years? mass: Another method measures the speed of gas moving past the black hole. In the given equation, v is the velocity of the gas (in kilometers per second), r is the distance of the gas cloud from the black hole (in kilometers), and G is Newton's gravitational constant. In this equation, G = 1.33 ×…arrow_forwardGM What is the orbital period of a bit of matter in an accretion disk that is located 3 x 105 km from a 29 M. black hole? (Hint: Use the circular orbit velocity formula, V. = Varrow_forwardPart 1. Stellar Mass Black Holes These are the collapsed cores of massive stars which end their life in supernova explosions. The stellar core can no longer use nuclear fusion to hold up the immense gravity, and collapses until its escape velocity rises higher than the speed of light. Voila! A black hole is formed. Part A: The Schwarzschild Radius The Schwarzschild Radius is defined as: 2GM (1) = c2 where r, is the Schwarzschild radius, G is the gravitational constant, M is the mass of the black hole, and c is the speed of light. 1. Let's say we have a black hole with a mass 10 times that of the Sun (the Sun's mass is 2 x 1030 kg, so the mass of the black hole is then 2 x 1031 kg). Using the definitions for G and c, what would the Schwarzschild radius of this black hole be? 2. If the radius of the Sun is 7 x 108 m, how does the black hole's radius compare? (Divide the radius of the Sun by the Schwarzschild radius). Your answer should be in the form of times smaller/bigger than the…arrow_forward
- What is the orbital period (in s) of a bit of matter in an accretion disk that is located 6 ✕ 105 km from a 99 M black hole? Hint: Use the circular orbit velocity formula, Vc = GM r . sarrow_forwardWhich of the below rotation curves best represents the orbital speeds stars in the Milky Way Galaxy would have if there were no dark matter in the galaxy? A B Distance Distance C D Distance Distance А.А В. В С. С D.D Velocity Velocity Velocity Velocityarrow_forward1. What would be the diameter (of the event horizon) of a black hole with the same mass as Jupiter? (2 points) answer: D BH ft m =arrow_forward
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