Horizons: Exploring the Universe (MindTap Course List)
14th Edition
ISBN: 9781305960961
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Chapter 14, Problem 4P
To determine
The average density of matter in the universe.
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Check out a sample textbook solutionStudents have asked these similar questions
Assume that the average galaxy contains 1011 MSun and that the average distance between galaxies is 10 million light-years. Calculate the average density of matter (mass per unit volume) in galaxies. What fraction is this of the critical density, 9.6 * 10-27?
Pretend that galaxies are spaced evenly, 7.0 Mpc apart, and the average mass of a galaxy is 1.0 ✕ 1011 M. What is the average density (in kg/m3) of matter in the universe? (Note: The volume of a sphere is 4/3pieR^3 and the mass of the sun is 2.0 ✕ 1030 kg.)
______ kg/m^3
Which model universe does this density value support?
A: open
B: flat
C: closed
why do you have to know the distance to a galaxy to find its mass?
Chapter 14 Solutions
Horizons: Exploring the Universe (MindTap Course List)
Ch. 14 - How does the darkness of the night sky tell you...Ch. 14 - How can Earth be located at the center of the...Ch. 14 - Prob. 3RQCh. 14 - Prob. 4RQCh. 14 - Why couldn’t atomic nuclei exist when the e of the...Ch. 14 - Why are measurements of the present density of the...Ch. 14 - Prob. 7RQCh. 14 - Prob. 8RQCh. 14 - What is the evidence that the Universe was very...Ch. 14 - Prob. 10RQ
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- According to Hubble’s law, what is the recessional velocity of a galaxy that is 108 light-years away from us? (Assume a Hubble constant of 22 km/s per million light-years.)arrow_forwardAssume that the average galaxy contains 1011MSunand that the average distance between galaxies is 10 million light-years. Calculate the average density of matter (mass per unit volume) in galaxies. What fraction is this of the critical density we calculated in the chapter?arrow_forwardIf we now realize dwarf ellipticals are the most common type of galaxy, why did they escape our notice for so long?arrow_forward
- In what ways are active galaxies like quasars but different from normal galaxies?arrow_forwardGiven the ideas presented here about how galaxies form, would you expect to find a giant elliptical galaxy in the Local Group? Why or why not? Is there in fact a giant elliptical in the Local Group?arrow_forwardCould the Milky Way ever become an active galaxy? Is it likely to ever be as luminous as a quasar?arrow_forward
- If the diameter of the Milky Way Galaxys visible disk, 80,000 ly, is represented in a model by a dinner plate with a diameter of 10 inches, what is the model distance to galaxy M31, 2.6 millionly away? What is the model distance to the Virgo galaxy cluster, 16 Mpc away? (Convert answers to feet.)arrow_forwardUsing the information from Example 28.1, how much fainter an object will you have to be able to measure in order to include the same kinds of galaxies in your second survey? Remember that the brightness of an object varies as the inverse square of the distance.arrow_forwardWhen comparing two isolated spiral galaxies that have the same apparent brightness, but rotate at different rates, what can you say about their relative luminosity?arrow_forward
- What evidence can you give that we live in a galaxy?arrow_forwardWhen astronomers make maps of the structure of the universe on the largest scales, how do they find the superclusters of galaxies to be arranged?arrow_forwardWe have said that the Galaxy rotates differentially; that is, stars in the inner parts complete a full 360° orbit around the center of the Galaxy more rapidly than stars farther out. Use Kepler’s third law and the mass we derived in Exercise 25.19 to calculate the period of a star that is only 5000 light-years from the center. Now do the same calculation for a globular cluster at a distance of 50,000 light-years. Suppose the Sun, this star, and the globular cluster all fall on a straight line through the center of the Galaxy. Where will they be relative to each other after the Sun completes one full journey around the center of the Galaxy? (Assume that all the mass in the Galaxy is concentrated at its center.)arrow_forward
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