21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 21.3, Problem 21.3ACYU
To determine
The scale factor keeps track of.
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What happens when galaxies collide?
A. Star collisions will be rare but the shapes of the galaxies will be largely distorted.
B. The shapes of the galaxies will be largely distorted and many of the stars of one galaxy will collide with stars of the other galaxy.
C. The shapes of the galaxies will be distorted and many stars will collide with stars of the other galaxy, as well as with other stars in the same galaxy.
D. Star collisions will be rare and the two galaxies will just pass through each other without any changes.
Is the answer A? Thank you!
The largest structures in the universe are
a.
star clusters.
b.
galaxy clusters.
c.
galaxy superclusters.
d.
filaments and voids.
e.
galaxies.
Galaxy seeds around which galaxies, clusters, and walls grew may have been
a.
caused by hot dark matter.
b.
caused by baryons.
c.
the result of the separation of the electromagnetic and weak forces.
d.
the result of freezing water molecules shortly after the universe became transparent to photons.
e.
caused by microscopic random fluctuations in the infant universe.
Chapter 21 Solutions
21st Century Astronomy
Ch. 21.1 - Prob. 21.1CYUCh. 21.2 - Prob. 21.2CYUCh. 21.3 - Prob. 21.3ACYUCh. 21.3 - Prob. 21.3BCYUCh. 21.4 - Prob. 21.4CYUCh. 21 - Prob. 1QPCh. 21 - Prob. 2QPCh. 21 - Prob. 3QPCh. 21 - Prob. 4QPCh. 21 - Prob. 5QP
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- Starting with the determination of the size of Earth, outline a sequence of steps necessary to obtain the distance to a remote cluster of galaxies. (Hint: Review the chapter on Celestial Distances.)arrow_forwardDescribe the main distinguishing features of spiral, elliptical, and irregular galaxies.arrow_forwardHow many galaxies like our own would it take Laid edge-to-edge to reach the nearest galaxy? (Hint: See Problem 9.)arrow_forward
- Why did it take so long for the existence of other galaxies to be established?arrow_forward3. Suppose you measure the radial velocity of a galaxy to be 5,000 km/s. How far away is it?arrow_forwardThe evidence leads modern astronomers to conclude that at the cores of active galaxies are supermassive black holes with masses as high as a. ten solar masses. b. a thousand solar masses. c. a million solar masses. d. a billion solar masses.arrow_forward
- Which of the following statements about the different types (shapes) of galaxies are correct? (choose all that apply) whatever type a galaxy is at its birth, that’s what it will be for all time what type we see a galaxy to be just depends on the angle at which we happen to see it; all galaxies look roughly the same in shape all galaxies start out as ellipticals, but some later evolve to be spirals and irregulars collisions and mergers between galaxies can sometimes change a galaxy’s type (shape)arrow_forwardAn astronomer in an imaginary Universe observes a small patch of the sky (0.005% of the total) with very deep observations and finds one million galaxies. How many galaxies can they estimate to be present in the whole Universe? 10 billion 20 billion 50 billion O 70 billionarrow_forwardA star at a distance of 50000 light years from the center of a galaxy has an orbital speed of 100 km/s around the galactic center. What is the total mass of the galaxy located at distances smaller than 50000 light years from the center? A. 7.6 ×1010 solar masses B. 4.2 ×1011 solar masses C. 3.5 ×1010 solar masses D. 1.4 ×1011 solar masses Is the answer C? M = (r x v^2) / G = 50000 x 9.46e15 x (100000^2) / 6.67e-11 / 2e30 (the Sun's mass) = 3.55e10 solar massesarrow_forward
- We know that dark matter must exist in galaxies. If not, many of the stars in a galaxy would ... a.Expand and go supernova due to the expansion of the Universe b.Fly away from the galaxy because the stars’ velocities are so large, and the galaxy would not have enough gravity to hold onto them c.Orbit the center of the galaxy normally d.Spiral in toward the center of the galaxy because most of the galaxy’s mass would be toward the centerarrow_forwardThe theory that waves of compression move around the galaxy triggering star formation is called a. the flocculent theory. b. the spiral compression theory. c. the density wave theory. d. the differential rotation theory. e. none of the above.arrow_forwardWhat 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_forward
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