Ch. 12
Applying the Concepts

<See the back of the chapter.>

Questions for Thought
 
 1. 	A light year is a unit of distance defined as the distance light travels during one year. This distance is about 9.5×1012 km.

 3. 	The more massive a star, the higher the pressure at the core, and the faster the fusion reactions take place.  Therefore, in general, even though more massive stars have more fuel, they use it at such a rapid rate that the massive stars “burn out” more quickly than less massive stars. A star that has a mass of one twenty-fifth that of the Sun would last longer than both the Sun and a star sixty times as massive as the Sun.

 4. 	The Hertzsprung-Russell diagram is a plot of the temperatures of stars indicated by spectral type versus the brightness of the stars indicated by absolute magnitude.  The diagram shows that most stars fall close to a narrow diagonal band called the main sequence. The position of a star on this diagram suggests the star's mass and age.

10. 	Massive stars can fuse elements to create heavier elements up to iron. If the stars are sufficiently massive to undergo a supernova, the energy released in the supernova 	explosion can fuse atoms to make even heavier elements.

12. 	The Milky Way galaxy has a spherical concentration of stars at the center, called the galactic nucleus, surrounded by a rotating disk of stars. This disk has the appearance of arms spiraling out from the nucleus. A spherical galactic halo of globular clusters of stars surrounds the main concentration of stars in the disk and nucleus. The galactic disk is the primary region of star formation because the bulk of the dust and gas are located there.

<Attached Questions>

 1.  T
 2.  F
 3.  F
 4.  T
 5.  F
 6.  T
 7.  T
 8.  T
 9.  F
10.  F

11. 	b
12. 	b
13. 	a
14. 	c
15. 	b
16. 	b
17. 	d
18. 	a
19. 	d
20. 	c
21. 	a
22. 	d
23. 	b
24. 	a
25. 	b