Question

5) A star (no matter what its mass) spends most of its life

Select one: a. as a protostar.

b. as a main-sequence star.

c. as a planetary nebula.

d. as a red giant or supergiant.

6) What is the ultimate fate of an isolated white dwarf?

Select one:

a. It will cool down and become a cold black dwarf.

b. As gravity overwhelms the electron degeneracy pressure, it will explode as a nova.

c. As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova.

d. As gravity overwhelms the electron degeneracy pressure, it will become a neutron star.

7) A typical neutron star is more massive than our Sun and about the size (radius) of

Select one:

a. a small asteroid (10 km in diameter).

b. Earth.

c. the Moon.

d. Jupiter.

8) What causes the radio pulses of a pulsar?

Select one: a. The star vibrates.

b. As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.

c. The star undergoes periodic explosions of nuclear fusion that generate radio emission.

d. The star's orbiting companion periodically eclipses the radio waves emitted by the main pulsar.

9) How does a black hole form from a massive star?

Select one:

a. During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole.

b. Any star that is more massive than 8 solar masses will undergo a supernova explosion and leave behind a black-hole remnant.

c. If enough mass is accreted by a white-dwarf star so that it exceeds the 1.4-solar-mass limit, it will undergo a supernova explosion and leave behind a black-hole remnant.

d. A black hole forms when two massive main-sequence stars collide.

10) Which of the following is not true about differences between novae and supernovae?

Select one: a. Novae are much less luminous than supernovae.

b. Supernovae eject gas into space but novae do not.

c. Novae occur only in binary star systems, while supernovae can occur both among single stars and among binary star systems.

d. The same star can undergo novae explosions more than once, but can undergo only a single supernova.

Answer 1

(5) b. as a main sequence star.

(6) c. As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova.

(7) a. a small asteroid (10 km in diameter).

(8) b. As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.

(9) a. During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole.

(10) d. The same star can undergo novae explosions more than once, but can undergo only a single supernova.