Stellar Remnants - Quiz 14

1. Which of the following has a radius (linear size) closest to that a neutron star?
A).. The Sun.
B)..The Earth.
C).. A basketball.
D)..A small city.
E)..A gymnasium.

2. What evidence leads astronomers to believe that they have detected black holes?
A)...They have seen tiny dark spots drift across the face of some distant stars.
B)... They have detected pulses of ultraviolet radiation coming from within black holes.
C)... They have seen x-rays, perhaps from gas around a black hole, suddenly disappear as a companion star eclipses the hole.
D)...They have seen a star suddenly disappear as it was swallowed by a black hole.
E)...They have looked into a black hole with x-ray radar telescopes.

3. What causes the radio pulses of a pulsar?
A)... The star vibrates.
B)...As the star spins, beams of radio radiation from it sweep through space. If one of these beams points toward the Earth, we observe a pulse.
C)... The star undergoes nuclear explosions that generate radio emission.
D)... The star's dark orbiting companion periodically eclipses the radio waves emitted by the main star.
E)... A black hole near the star absorbs energy from it and reemits it as radio pulses.

4. If mass is added to a white dwarf,
A)... its radius increases.
B)... its radius decreases.
C)... its density increases
D)... it may exceed the Chandrasekhar limit and collapse.
E)... all of the above except (a).

5. The Schwarzschild radius of a body is
A)... the distance from its center at which nuclear fusion ceases.
B)... the distance from its surface at which an orbiting companion will be broken apart.
C)... the maximum radius a white dwarf can have before it collapses.
D)... the maximum radius a neutron star can have before it collapses.
E)...the radius of a body at which its escape velocity equals the speed of light.

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