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 19, Problem 53EAP
Mass of the Central Black Hole. Suppose you observe a star orbiting the galactic center at a speed of 1000 km/s in a circular orbit with a radius of 20 light-days. Calculate the mass of the object the star is orbiting.
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Astronomers now think that there is a black hole with more than 4 milliion times the mass of our Sun at the center of our galaxy?
Roughly how large would the event horizon of such a supermassive black hole be?
a. the size of our moon
b. about 4 light years across
c. about 17 times the size of our sun
d. about the size of an atom (so much mass really compresses the event horizon)
e. this question can't be answered without knowing what kind of stars were swallowed by the black hole
What makes us think that the star system Cygnus X-1 contains a black hole?
A, It emits X rays characteristic of an accretion disk, but the unseen star in the system is too
massive to be a neutron star.
B. No light is emitted from this star system, so it must contain a black hole.
C. The fact that we see strong X-ray emission tells us that the system must contain a black
hole.
D.Cygnus X-1 is a powerful X-ray burster, so it must contain a black hole.
The Tully-Fischer method relies on being able to relate the mass of a galaxy to its rotation velocity. Stars in the outer-most regions of the Milky Way galaxy, located at a distance of 50 kpc from the galactic centre, are observed to orbit at a speed vrot = 250 km s−1. Using Kepler’s 3rd Law, determine the mass in the Milky Way that lies interior to 50 kpc. Express your answer in units of the Solar mass.
Chapter 19 Solutions
The Cosmic Perspective (9th Edition)
Ch. 19 - Prob. 1VSCCh. 19 - Prob. 2VSCCh. 19 - Prob. 3VSCCh. 19 - Prob. 4VSCCh. 19 - Prob. 5VSCCh. 19 - Prob. 6VSCCh. 19 - Prob. 1EAPCh. 19 - Prob. 2EAPCh. 19 - Prob. 3EAPCh. 19 - Prob. 4EAP
Ch. 19 - Prob. 5EAPCh. 19 - Prob. 6EAPCh. 19 - Prob. 7EAPCh. 19 - Prob. 8EAPCh. 19 - Prob. 9EAPCh. 19 - Prob. 10EAPCh. 19 - Prob. 11EAPCh. 19 - Prob. 12EAPCh. 19 - Prob. 13EAPCh. 19 - Prob. 14EAPCh. 19 - Prob. 15EAPCh. 19 - Prob. 16EAPCh. 19 - Prob. 17EAPCh. 19 - Does It Make Sense? Decitie whether the statement...Ch. 19 - Prob. 19EAPCh. 19 - Prob. 20EAPCh. 19 - Prob. 21EAPCh. 19 - Prob. 22EAPCh. 19 - Prob. 23EAPCh. 19 - Prob. 24EAPCh. 19 - Prob. 25EAPCh. 19 - Prob. 26EAPCh. 19 - Prob. 27EAPCh. 19 - Prob. 28EAPCh. 19 - Prob. 29EAPCh. 19 - Prob. 30EAPCh. 19 - Choose the best answer to each of the following....Ch. 19 - Prob. 32EAPCh. 19 - Prob. 33EAPCh. 19 - Prob. 34EAPCh. 19 - Prob. 35EAPCh. 19 - Prob. 36EAPCh. 19 - Prob. 37EAPCh. 19 - Prob. 39EAPCh. 19 - Prob. 40EAPCh. 19 - Prob. 41EAPCh. 19 - Prob. 42EAPCh. 19 - Prob. 44EAPCh. 19 - Prob. 45EAPCh. 19 - Prob. 46EAPCh. 19 - Prob. 47EAPCh. 19 - Prob. 48EAPCh. 19 - Prob. 49EAPCh. 19 - Prob. 50EAPCh. 19 - Prob. 52EAPCh. 19 - Mass of the Central Black Hole. Suppose you...Ch. 19 - Prob. 54EAPCh. 19 - Prob. 55EAPCh. 19 - Prob. 56EAPCh. 19 - Prob. 57EAPCh. 19 - Prob. 58EAPCh. 19 - The Speed of Supernova Debris. The kinetic energy...
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- 7. How large is our supermassive black hole in terms of the size of the Earth’s orbit? (Divide the radius of Sagittarius A* (i.e., your result in Question 6) in meters by 1 AU(1 AU =1.5 x 1011 m) to see how large our supermassive black hole is in terms of the size of the Earth’s orbit. Note that the size of Earth’s orbit is defined as 1 AU). Your result will be in AU (Just submit your answer, do not submit the unit AU).arrow_forwardObservations of the central region of the galaxy M87 indicate that stars which are 60 light years from the centre are orbiting the central supermassive black hole at speeds of 730 kms‑1. Estimate the mass of the black hole, in solar masses. (You can assume circular motion.arrow_forwardWhat 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_forward
- 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!arrow_forwardThe Tully-Fischer method relies on being able to relate the mass of a galaxy to its rotation velocity. Stars in the outer-most regions of the Milky Way galaxy, located at a distance of 50 kpc from the galactic centre, are observed to orbit at a speed vrot determine the mass in the Milky Way that lies interior to 50 kpc. Express your answer in units of the Solar mass. 250 km s-1. Using Kepler's 3rd Law,arrow_forward(Astronomy) PSR1913+16 Problem II. Using only the Figure, what are the maximum radial velocities as found from the redshift and blueshift, respectively? Note: redshifts have positive radial velocities values in the figure, whereas blueshifts have negative radial velocity values. (Answer in km/s)arrow_forward
- Estimating the mass of the Milky Way a) Assuming the Sun moves in a circular orbit of radius 8 kiloparsecs around the center of the Milky Way, and that its orbital speed is 220 km/s, calculate how many years it takes the Sun to complete one orbit of the Galaxy. Remember to convert kiloparsecs to kilometers. b) Using the modified form of Kepler's third law (introduced in Lecture 13, for measuring the combined masses of binary stars), R³ m+ M = estimate the mass of the Milky Way enclosed within 8 kpc (Sun's orbit radius). The mass of the Milky Way inside p² I the Sun's orbit can be represented as a single mass (M) located at its center, and the mass of the Sun (m) can be considered infinitesimally small compared to the Milky Way's (i.e., m < M). c) Is this estimate of the Milky Way's mass an upper or lower limit? Explain your reasoning.arrow_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_forwardAn 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!arrow_forward
- What is the only viable explanation for so much mass in so small a region at the core of our galaxy? a. a tight cluster of stars b. many neutron stars c. many stellar black holes d. a single massive black hole e. none of the abovearrow_forwardThe 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_forwardOnce again in this chapter, we see the use of Kepler’s third law to estimate the mass of supermassive black holes. In the case of NGC 4261, this chapter supplied the result of the calculation of the mass of the black hole in NGC 4261. In order to get this answer, astronomers had to measure the velocity of particles in the ring of dust and gas that surrounds the black hole. How high were these velocities? Turn Kepler’s third law around and use the information given in this chapter about the galaxy NGC 4261-the mass of the black hole at its center and the diameter of the surrounding ring of dust and gas-to calculate how long it would take a dust particle in the ring to complete a single orbit around the black hole. Assume that the only force acting on the dust particle is the gravitational force exerted by the black hole. Calculate the velocity of the dust particle in km/s.arrow_forward
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