Extreme Objects in Our Galaxy Practice Problems

Review the following concepts if needed:

• Matter and Antimatter Help
• Black Holes Help
• Pulsars Help
• Black Dwarfs and Neutron Stars Help

Extreme Objects in Our Galaxy Practice Problems

A good score is 8 correct. Answers are given at the end.

1. Photons are

(a) antiprotons.

(b) antielectrons.

(c) antineutrons.

(d) energy packets.

2. As a black hole swallows up more and more matter,

(a) its mass decreases.

(b) the gravitational radius decreases.

(c) its mass increases.

(d) None of the above

3. The waveforms of the pulses from a pulsar are

(a) smooth.

(b) irregular.

(c) long.

(d) short.

4. If an object collapses so that its radius is less than the Schwarzchild radius, then

(a) things can come out but cannot go in.

(b) the escape velocity at the surface is greater than the speed of light.

(c) the escape velocity at the surface is less than the speed of light.

(d) the object is, by definition, a pulsar.

5. Radio waves travel through interstellar space at a slightly different speed than visible light because of

(a) magnetic fields.

(b) differences in photon energy.

(c) dispersion.

(d) No! Radio waves always travel through interstellar space at precisely the same speed as visible light.

6. Suppose that a neutron somehow forms, and it is floating all by itself in space. How long can we expect it to last?

(a) Forever

(b) Until it collapses into a black hole

(c) Until it becomes part of a neutron star

(d) none of the above.

7. The EM energy from pulsars is believed to be a product of

(a) neutrons decaying into energy.

(b) matter interacting with antimatter.

(c) electrons rising into higher orbits.

(d) none of the above.

8. As a rotating white dwarf dies out and collapses into a neutron star,

(a) it rotates faster and faster.

(b) it rotates more and more slowly.

(c) its rotational speed does not change.

(d) rotation loses meaning because of the incalculable density of the object.

9. Suppose that a 1,000-kg spacecraft from Earth touches down on a planet and that planet turns out to be antimatter. What will happen?

(a) There will be an explosion of incalculable violence, and all the matter in both the planet and the spacecraft will be annihilated.

(b) There will be an explosion, and approximately 90 quintillion (9.0 × 10 ¹⁹ ) joules of energy will be liberated.

(c) There will be an explosion, and approximately 180 quintillion (1.80 × 10 ²⁰ ) joules of energy will be liberated.

(d) The spacecraft will be quietly swallowed up by the planet and will disappear.

10. When an electron moves into a larger orbit within an atom,

(a) the electron’s energy increases.

(b) the electron’s energy decreases.

(c) the electron’s charge increases.

(d) the electron’s charge decreases.

Answers

1. D

2. C

3. B

4. B

5. C

6. D

7. D

8. A

9. C

10. A