Loose Leaf For Explorations: Introduction To Astronomy
9th Edition
ISBN: 9781260432145
Author: Thomas T Arny, Stephen E Schneider Professor
Publisher: McGraw-Hill Education
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Chapter 17, Problem 4TQ
To determine
The distance required to travel to see one’s mother’s childhood; the distance required to travel to see astronomers of ancient Egypt; Relation of both the cases from the study of young galaxies now.
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Students have asked these similar questions
Astronomers recently claimed to have discovered the most distant galaxy known. How would they have determine this distance?
If a galaxy is 8.9 Mpc away from Earth and recedes at 497 km/s, what is H. (in km/s/Mpc)?
km/s/Mрс
What is the Hubble time (in yr)?
years
How old (in yr) would the universe be, assuming space-time is flat and the expansion of the universe has not been accelerating?
years
How would acceleration change your answer?
If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above.
If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.
Using our example from the previous unit, let's try to determine the Hubble time for this example universe. You were given that a good representative galaxy receded at a speed of 4000 km/s and was found to be 20 Mpc away. With that in mind, what would the age of that universe be in years (aka what is that universe's Hubble time)? Go ahead and take the number of kilometers per Mpc to be approximately 3.1*10^19 km/Mpc. While this problem may look scary at first, this is really just bringing you full circle to one of the unit conversion problems you encountered at the beginning of this course.
Chapter 17 Solutions
Loose Leaf For Explorations: Introduction To Astronomy
Ch. 17 - Prob. 1QFRCh. 17 - Prob. 2QFRCh. 17 - Prob. 3QFRCh. 17 - Prob. 4QFRCh. 17 - (17.3) Why are galaxy collisions of interest?Ch. 17 - Prob. 6QFRCh. 17 - Prob. 7QFRCh. 17 - Prob. 8QFRCh. 17 - Prob. 9QFRCh. 17 - Prob. 10QFR
Ch. 17 - Prob. 11QFRCh. 17 - Prob. 12QFRCh. 17 - Prob. 13QFRCh. 17 - Prob. 14QFRCh. 17 - Prob. 15QFRCh. 17 - Prob. 16QFRCh. 17 - Prob. 17QFRCh. 17 - Prob. 18QFRCh. 17 - Prob. 19QFRCh. 17 - Prob. 20QFRCh. 17 - Prob. 21QFRCh. 17 - Prob. 22QFRCh. 17 - Prob. 1TQCh. 17 - Prob. 2TQCh. 17 - Prob. 3TQCh. 17 - Prob. 4TQCh. 17 - Prob. 5TQCh. 17 - Prob. 6TQCh. 17 - Prob. 1PCh. 17 - Prob. 2PCh. 17 - Prob. 3PCh. 17 - Prob. 4PCh. 17 - Prob. 5PCh. 17 - Prob. 6PCh. 17 - Prob. 7PCh. 17 - Prob. 8PCh. 17 - Prob. 9PCh. 17 - Prob. 10PCh. 17 - Prob. 1TYCh. 17 - Prob. 2TYCh. 17 - Prob. 3TYCh. 17 - Prob. 4TYCh. 17 - Prob. 5TYCh. 17 - Prob. 6TYCh. 17 - Prob. 7TYCh. 17 - Prob. 8TYCh. 17 - Prob. 9TYCh. 17 - Prob. 10TY
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- A galaxy with a spherically symmetric distribution of matter has a mass density profile of the type p(r) ∞ 1/r, where r is the radial coordinate from the centre of the galaxy. To what type of circular velocity (r) does this correspond? Select one: a. (r) O b. c. O d. (r) ~ r (r) ~ √r (r): = constantarrow_forwardA galaxy's rotation curve is a measure of the orbital speed of stars as a function of distance from the galaxy's centre. The fact that rotation curves are primarily flat at large galactocen- tric distances (vrot(r) ~ constant) is the most common example of why astronomer's believe dark matter exists. Let's work out why! Assuming that each star in a given galaxy has a circular orbit, we know that the accelera- tion due to gravity felt by each star is due to the mass enclosed within its orbital radius r and equal to v?/r. Here, ve is the circular orbit velocity of the star. (a) Show that the expected relationship between ve and r due to the stellar halo (p(r) xr-3.5) does not produce a flat rotation curve. (b) Show that a p(r) ∞ r¯² density profile successfully produces a flat ro- tation curve and must therefore be the general profile that dark matter follows in our galaxy.arrow_forwardHow astronomers determine the distance of a galaxy? Explain.arrow_forward
- 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!arrow_forwardIt is possible to derive the age of the universe given the value of the Hubble constant and the distance to a galaxy, again with the assumption that the value of the Hubble constant has not changed since the Big Bang. Consider a galaxy at a distance of 235 million light-years receding from us at a velocity, v. If the Hubble constant is 20.5 km/s per million light-years, what is its velocity? (Enter the magnitude in km/s.) _________ km/sarrow_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 = 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.arrow_forward
- The Andromeda Galaxy is a member of the Local Group of galaxies. It is approaching us. Does this mean that the Hubble Law is wrong? Why or why not? Explain.arrow_forwardA Type la supernova explodes in a galaxy at a distance of 6.10×107 light-years from Earth. If astronomers detect the light from the supernova today, how many years T have passed since the supernova exploded? T= 2.07 x10 -5 years Given a Hubble constant of 74.3 km/s/Mpc, at what speed v is this galaxy moving away from Earth? v= km/s What is this galaxy's redshift? redshift:arrow_forwardIt can be shown that if an object orbiting a star of mass M in a circular orbit of radius R has speed v, then Rv? M Suppose a star orbits the center of the galaxy it is contained in with an orbit that is nearly circular with radius 18 R = 2.5 x 10 and velocity v = 230 km/s. Use the result above to estimate the mass of the portion of the galaxy inside the star's orbit (place all of this mass at the center of the orbit). Mass =arrow_forward
- It is possible to derive the age of the universe given the value of the Hubble constant and the distance to a galaxy, again with the assumption that the value of the Hubble constant has not changed since the Big Bang. Consider a galaxy at a distance of 400 million light-years receding from us at a velocity, v. If the Hubble constant is 20 km/s per million light-years, what is its velocity? How long ago was that galaxy right next door to our own Galaxy if it has always been receding at its present rate? Express your answer in years. Since the universe began when all galaxies were very close together, this number is a rough estimate for the age of the universe.arrow_forwardBased on your analysis of galaxies in Table 26.1, is there a correlation between the population of stars and the quantity of gas or dust? Explain why this might be.arrow_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_forward
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