Chelsea Esposito's Quiz

Chelsea Esposito

1. What is a white dwarf?
White dwarfs are the remaining cores of dead stars. Electron degeneracy pressure supports them against
gravity.

2. What can happen to a white dwarf in a close binary system?
A star that started with less mass gains mass from its companion. Eventually the mass-losing star will
become a white dwarf.

3. What is a neutron star?
A ball of neutrons left over from a massive star supernova and supported by neutron degeneracy pressure.

4. How were neutron stars discovered?
Beams of radiation from a rotating neutron star sweep through space like lighthouse beams, making them
appear to pulse. Observations of these pulses were the first evidence for neutron stars.

5. What can happen to a neutron star in a close binary system?
The accretion disk around a neutron star gets hot enough to produce X-rays, making the system an X-ray
binary. Sudden fusion events periodically occur on a the surface of an accreting neutron star, producing X-
ray bursts.

6. What is a black hole?
A black hole is a massive object whose radius is so small that the escape velocity exceeds the speed of light

7. What would it be like to visit a black hole?
You can orbit a black hole like any other object of the same mass. Near the event horizon time slows down
and tidal forces are very strong.

8. Do black holes really exist?
Some X-ray binaries contain compact objects to massive to be neutron stars, they are almost certainly black
holes.

9. What causes gamma ray bursts?
Most gamma-ray bursts come from distant galaxies. They must be among the most powerful explosions in
the universe, probably signifying the formation of black holes. At least some gamma-ray bursts come from
supernova explosions.

10. What did Jocelyn Bell discover?
She discovered the first radio pulsars.