Chapter 13 Quiz Jessica Brandon

1.     What is a white dwarf?

A white dwarf is the core left over from a low-mass star, supported against the crush of gravity by electron degeneracy pressure.

2.     What can happen to a white dwarf in a close binary system

A white dwarf in a close binary system can acquire hydrogen from its companion through an accretion disk. As hydrogen builds up on the white dwarf’s surface, it may ignite with nuclear fusion to make a nova.

3.     What is a neutron star?

A neutron star is the ball of neutrons created by the collapse of the iron core in a massive star supernova.

4.     How were neutron stars discovered?

Neutron stars spin rapidly when they are born, and their strong magnetic fields can direct beams of radiation that sweep through space as the neutron star spins. We see such neutron stars as pulsars, and these pulsars provided the first direct evidence for the existence of neutron stars.

5.     What can happen to a neutron star in a close binary system?

Neutron stars in close binary systems can accrete hydrogen from their companions, forming dense, hot accretion disks. The hot gas emits strongly in X rays, so we see these systems as X-ray binaries. In some of these systems, frequent bursts of helium fusion ignite on the neutron star’s surface, emitting X-ray bursts.

6.     What is a black hole?

A black hole is a place where gravity has crushed matter into oblivion, creating a true hole in the universe from which nothing can ever escape, not even light.

7.     What would it be like to visit a black hole?

Time would seem to run slowly for the object. Its light would be increasingly redshifted as it approached the black hole. The object would never quite reach the event horizon, but it would soon disappear from view as its light became so redshifted that no instrument could detect it.

8.     Do black holes really exist?

No known force can stop the collapse of a stellar corpse with a mass above the neutron star limit of 2 to 3 solar masses, and theoretical studies of supernovae suggest that such objects should sometimes form. Observational evidence supports this idea.

9.     What causes gamma ray bursts?

Gamma-ray bursts occur in distant galaxies and are the most powerful bursts of energy we observe anywhere in the universe. No one knows their precise cause, although at least some appear to come from unusually powerful supernovae.

10. What did Jocelyn Bell discover? 

She discovered the first neutron star by using a radio telescope. She notices a very regular pulses of radio emission coming from a single part of the sky.