Module 16

Question 1

1a. Define: nuclear fusion

Answer 1

the process by which two or more small nuclei fuse to make a bigger nucleus

Question 2

1b. Define: nuclear fission

Answer 2

the process by which a large nucleus is split into smaller nuclei

Question 3

1c. Define: critical mass

Answer 3

the amount of isotope necessary to sustain a chain reaction

Question 4

1d. Define: absolute magnitude

Answer 4

The brightness of a star, corrected for distance, on a scale of -8 to +19. The smaller the number, the brighter the star.

Question 5

1e. Define: apparent magnitude

Answer 5

The brightness of a star as seen in the night sky. The smaller the number the brighter the star.

Question 6

1f. Define: light year

Answer 6

the distance light could travel along a straight line in one year

Question 7

1g. Define: galaxy

Answer 7

a large ensemble of stars, all interacting through the gravitational force and orbiting around a common center

Question 8

2. From the inside to the outside, name the four regions of the sun.

Answer 8

the core, the radiative zone, the convection zone, and the photosphere

Question 9

3. How does the sun get its power? In which region of the sun does this process occur?

Answer 9

the sun gets its power from nuclear fusion that occurs in the core

Question 10

4. What part of the sun do we see?

Answer 10

the photosphere

Question 11

5. A (251Cf) nucleus is bombarded with a neutron. It breaks down into a (124 Sn) nucleus, a (120Cd) nucleus and seven neutrons. Is this nuclear fission or nuclear fusion?

Answer 11

nuclear fission

Question 12

6. Two (4He nuclei collide and turn into a (7Be) nucleus and one neutron. Is this nuclear fusion or nuclear fission?

Answer 12

nuclear fusion

Question 13

7. For both the nuclear fusion that occurs in the sun and the nuclear fission that occurs in a nuclear power plant, what can we say about the mass of the starting materials compared to the mass of what’s made in the end?

Answer 13

the mass of the starting materials is larger than the mass of the materials the process makes

Question 14

8. Why is it impossible for a nuclear power plant to have a nuclear explosion?

Answer 14

a power plant does not have significantly more than the critical mass of the large nucleus that is breaking apart

Question 15

9. Why is nuclear fusion considered a better option for energy production than nuclear fission?

Answer 15

Nuclear fusion is a better means of producing energy because there are no radioactive byproducts, there is no chance of meltdown, and the starting materials are cheap.

Question 16

10. If nuclear fusion is a better option, why don’t we use it?

Answer 16

We cannot use nuclear fusion yet because we cannot master the technology to make it economically feasible.

Question 17

11. look in book on page 421, #11

Answer 17

a- Red Giant b-Main Sequence c- Supergiant d-White Dwarf

Question 18

12. look in book on page 422, #12

Answer 18

star (b) is most like our sun

Question 19

13. look in book on page 422, #13

Answer 19

(d), (b), (a) and (c)

Question 20

14. look in book on page 422, #14

Answer 20

(d), (b), (a), and (c)

Question 21

15. look in book on page 422, #15

Answer 21

(a) is the coolest

Question 22

16. What similarity exists between novas, supernovas and pulsating variables?

Answer 22

all three of these are variable star types; thus, their brightness changes radically with time

Question 23

17. What is the big difference between novas, supernovas, and pulsating variables?

Answer 23

The big difference between these star types is lifetime. Pulsating stars last a long time, supernovas exist very briefly, and novas are somewhere in between.

Question 24

18. What most likely formed the crab nebula?

Answer 24

most likely formed by a supernova

Question 25

19. What are the two methods for measuring the distance from earth to a star? Which of the two is most accurate? Which can be used to measure long distances?

Answer 25

The two methods are the parallax method andf the apparent magnitude method. The parallax method is exact, but the apparent magnitude method can be used to measure longer distances.

Question 26

20. Why are Cepheid variables so important for measuring long distances in the universe?

Answer 26

Cepheid variables are important for measuring long distances because they seem to have a relationship between their period and their magnitude. That allows them to be used in hte apparent magnitude method for measuring long distances in the universe.

Question 27

21. What are the four basic types of galaxies? To which type does the Milky Way belong?

Answer 27

spiral, lenticular, elliptical, and irregular; the Milky Way is a spiral galaxy

Question 28

22. Fill in the blanks: stars group together to form—, which group together to form—-, which group together to form—-, some of which group together to form——–.

Answer 28

galaxies…groups…clusters… superclusters

Question 29

23. For the first three answers you gave in #22, give the names that apply to those in which earth’s solar system belongs.

Answer 29

Milky Way….Local Group…Virgo Cluster

Question 30

24. Why do most astronomers believe that universe is expanding?

Answer 30

Most astronomers believe that the universe is expanding because the light from nearly every galaxy experiences a red shift before it reaches the earth, and the red shift increases the farther the galaxy is from the earth.

Question 31

25. If the universe is expanding, does the geometry of the expansion matter? If so, why?

Answer 31

Yes, the geometry of the universla expansion makes a great deal of difference. The theories that can be developed for the fromation of the universe depend on that initial assumption.