Lecture on Stellar Evolution and Black Holes

These flashcards cover the core concepts of stellar evolution, black holes, and associated phenomena based on the lecture transcript.

What are white dwarfs?

White dwarfs are the remaining cores of dead stars.

What supports white dwarfs against gravity?

Electron degeneracy pressure supports white dwarfs against gravity.

What is the white dwarf limit?

The white dwarf limit (Chandrasekhar limit) is approximately 1.4 solar masses, beyond which no white dwarf can exist.

What happens to a white dwarf in a close binary system?

It can gain mass from its companion, eventually leading to phenomena like novae or supernovae.

What is a nova?

A nova is a temporary brightening of a star system caused by the sudden onset of hydrogen fusion on a white dwarf's surface.

What triggers a supernova in a massive star?

The collapse of the iron core of a massive star at the white dwarf limit.

How are supernovae different from novae?

Supernovae result in complete explosion of the white dwarf, while novae only eject surface matter and leave the white dwarf intact.

What is a neutron star?

A neutron star is a dense ball of neutrons left behind after a massive-star supernova.

How was the neutron star first discovered?

It was discovered in 1967 by Jocelyn Bell, who noticed regular pulses of radio emission from a pulsar.

What is a pulsar?

A pulsar is a neutron star that beams radiation along its magnetic axis, which is not aligned with its rotation axis.

What is the escape velocity at the event horizon of a black hole?

At the event horizon, the escape velocity equals the speed of light, preventing anything from escaping.

What occurs during a black hole merger?

Two black holes merging produces bursts of gravitational waves.

What are gamma-ray bursts associated with?

Gamma-ray bursts are likely associated with the formation of black holes and supernova explosions.

What happens when a neutron star accretes matter?

Accreting matter can lead to an increase in spin, and sudden fusion events can produce X-ray bursts.

Describe the significance of gravitational waves.

Gravitational waves provide a new way to observe the universe and were first detected by LIGO.