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 36EAP
To determine
To discuss: An important but unanswered question related to galaxy evolution.
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Describe what is meant by Olbers’ paradox. Explain how it is solved by our modern understanding of the Universe.
The Milky Way grew through merging with many smaller galaxies. What are the observational signatures of this process?
O The motion of old stars in the bulge and halo of our galaxy are randomly orientated, meaning they were formed from collisions of small,
accreted, galaxies all on different paths.
O The ordered motion of the bulge / halo stars means that they came from many objects.
The random motions of stars in the disk means it was formed from collisions of small, accreted, galaxies.
O The motion of young stars in the disk are all in the same direction, meaning they came in as seperate objects.
Hubble's law. Hubble found that distant galaxies are receding with a velocity proportional to their distance from where we are on Earth. For the ith Galaxy, vi=H0ri
With us at the origin. Show that this recession of the galaxies from us does not imply that we are at the center of the universe. Specifically, take the Galaxy at r1 as a New origin and show that Hubble's law is still obeyed.
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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- Which of the following statements best describes our galaxy, the Milky Way? O A bulge dominated system, with little or no disk, approximately 27,000 light years across. A disk 100,000 lightyears across filled with gas and stars, with a bulge of older stars in the galaxy centre. A disk 27,000 light years across with a bulge of gas and newly formed stars in the galaxy centre. O A spherical (elliptical) galaxy, 100,000 lightyears across, with no gas and no new stars.arrow_forwardWrite down the Doppler formula for light as an equation. Explain each letter's meaning. Then compute what the relative change in the wavelength of emitted light would be for a galaxy moving at a velocity 11.12 thousand kilometers per second away from Earth.arrow_forward18 If we develop spacecraft that can take humans to nearby solar systems at a few percent of the speed of light, how long would it be before we could conceivably populate all habitable planets in the entire Milky Way? A B D E A few hundred thousand years A few hundreds of millions of years We could never colonize the galaxy unless we had ships that could travel very close to the speed of light. A few million years A few billion yearsarrow_forward
- When we observe the most distant galaxies what are we looking at? At galaxies with ages similar to that of the Milky Way, because light travels so quickly that there is no significant time delay. Because of the finite speed of light, we are observing how galaxies looked like in the past. Because of the finite speed of light, we have the opportunity to observe our own galaxy when it started forming in the past. Because of the long light travel time, we are observing old galaxies.arrow_forwardHubble's First Attempt. Edwin Hubble's first attempt to measure the universe's expansion rate was flawed because the standard candles he was using were not properly calibrated. Look at (Figure 1) a.Estimate the value of Ho corresponding to the solid line in the figure. Express your answer kilometers per second per million light-years to two significant figures. b.What is the approximate age of the universe indicated by that erroneous value of Ho? Express your answer in years to one significant figure.arrow_forwardAstronomers frequently say that "there are more stars in the universe than there are grains of sand on all the beaches on the earth". Given that a typical grain of sand is about 0.5 – 1.0 mm in diameter, estimate the number of grains of sand on all the earth's beaches. The diameter of the Earth is 12,742 km. a) About 1011 b) About 1016 c) About 1021. 6. Assume that a typical galaxy contains about 200 billion stars and that there are more than 150 billion galaxies in the known universe. Estimate the total number of stars in the universe. b) About 1022 a) About 1010 c) About 1016. 7. Compare the values of the number of grains of sand in all earth's beaches (from problem 5) with the number of stars in the universe (from problem 6) – which is greater? a) Number of sand grains b) number of stars c) they are about the same.arrow_forward
- Suppose astronomers discover a radio message from a civilization whose planet orbits a star 35 lightyears away. Their message encourages us to send a radio answer, which we decide to do. Suppose our governing bodies take 2 years to decide whether and how to answer. When our answer arrives there, their governing bodies also take two of our years to frame an answer to us. How long after we get their first message can we hope to get their reply to ours? (A question for further thinking: Once communication gets going, should we continue to wait for a reply before we send the next message?)arrow_forwardStuck on homework, especially the significant part. If the value of the Hubble constant is 70 kilometers per second per Mpc, then what is the Hubble time – that is, the amount of time the universe has been expanding since the Big Bang? Give your answer first in units of seconds, and then in units of billions of years. Your answer is significant to two digits.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
- What is cosmic infalation ? Explain it.arrow_forwardSuppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In this case, A. Galaxy 1 must be twice as big as Galaxy 2. B. we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2. C. we are seeing Galaxy 1 as it looked at a later time in the history of the universe than Galaxy 2. D. Galaxy 2 must be twice as old as Galaxy 1.arrow_forwardAs we discussed, clouds are made of a great many small drops. Really - a great many. Imagine a liquid cloud that fills a volume of 1 km3. The clouds contains 100 drops per cubic centimeter; for the sake of argument assume that each is 10 microns (micrometers) in radius. A. How many drops does the cloud contain? Compare this to a big number - say, the number of stars in the galaxy. B. What mass of water does the cloud contain? Compare this to something big - elephants, trucks, that sort of thing. C. What fraction of the cloud volume is filled with condensed water? One way to approach this is to compare the density of the suspended liquid water to the density of the surrounding air. D. How many 1 mm drizzle drops could you make from all the cloud drops? E. How much energy was released when this water condensed from vapor to liquid? If the water condensed in 20 minutes (a reasonable lifetime for a small cloud), what was the (energy per time)? powerarrow_forward
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