Test 2

d) 

1.	In the Hubble classification scheme for spiral galaxies, the tightness of the winding of the spiral arms appears to be related directly to
	A)	the age of the galaxy, as determined from the age of its individual stars.
	B)	the number of globular clusters in the halo of the galaxy.
	C)	the overall intrinsic size of the galaxy, or the diameter across the spiral arms.
	D)	the size of the central bulge of the galaxy.

2.	The typical diameter of a spiral galaxy is about
	A)	107 ly.
	B)	105 ly.
	C)	1 ly.
	D)	100 ly.

3.	What mechanism is believed to produce flocculent spiral galaxies?
	A)	Satellite galaxies plunging through the disk of the nuclear spiral galaxy
	B)	Self-propagating star formation, where star formation occurs in bursts
	C)	Shock waves from explosive star formation in the nuclear bulge
	D)	Density waves in the interstellar medium

4.	What mechanism is believed to produce grand-design spiral galaxies?
	A)	Shock waves from explosive star formation in the nuclear bulge
	B)	Density waves in the interstellar medium
	C)	Satellite galaxies plunging through the disk of the nuclear spiral galaxy
	D)	Self-propagating star formation, where star formation occurs in bursts

5.	What is the designation given to a galaxy with a large nuclear bulge and tightly wound arms starting from a bar through the nuclear bulge?
	A)	Sb
	B)	SBa
	C)	SBc
	D)	Sa

6.	How do most spiral galaxies rotate?
	A)	The arms lead as the galaxy rotates (arms point forward).
	B)	Spiral galaxies do not rotate; if they did, then the spiral pattern would soon disappear.
	C)	We do not know; they rotate far too slowly for us to have seen any motion in the time since galaxies were discovered.
	D)	The arms trail as the galaxy rotates (arms point backward). 7. What is believed to be the origin of starburst galaxies? A) The galaxies are slower rotators than other galaxies, so the slower-speed collisions between interstellar clouds produce more star formation. B) The galaxies are newly formed and are undergoing their initial, rapid star formation. C) A recent collision with another galaxy has triggered a wave of star formation. D) A recent series of supernovae has compressed the interstellar medium and started a wave of star formation. 8. What is believed to be the origin of giant elliptical galaxies? A) They formed that way and have remained unchanged ever since. B) They grew by devouring smaller galaxies. C) Collisions of galaxies in the cluster produces a smooth distribution of stars through the cluster, which sink to the center of the cluster and form giant galaxies there. D) They have grown continuously since their formation by accretion of intergalactic gas. 9. Which one of the following statements is true about clusters of galaxies? A) The observed mass of the galaxies of the cluster is many thousands of times too small to hold the cluster together. B) The observed mass of the galaxies of the cluster is about 10 times larger than the amount needed to hold the cluster together. C) The observed visible mass of the galaxies in the cluster is about 10 times too small to hold the cluster together. D) The observed mass of the galaxies of the cluster is almost exactly equal to that needed to hold the cluster together. 10. Many rich, regular clusters of galaxies contain substantial amounts of very hot, intergalactic gas. What is believed to have produced this hot gas? A) Collisions between galaxies in the cluster B) Bursts of star formation in merging galaxies C) Supernovae (exploding stars) D) Jets of gas ejected by supermassive black holes at the centers of the galaxies  1. D 2. B 3. B 4.B 5. B 6. D 7.C 8. B 9. C 10. A 1. 2. 3. 4. 5.   6. 7.   8. 9. 10..