07 Stellar Endings and Cosmic Recycling Free Online FlashCards

How does a Sun-like star become a white dwarf?

A Sun-like star sheds its outer layers, leaving a hot, compact core that gradually cools and fades without sustained fusion.

What supports a white dwarf, and what is its approximate mass limit?

Electron degeneracy pressure supports a white dwarf against gravity. It cannot remain stable above about 1.4 solar masses, the Chandrasekhar limit.

What happens to a white dwarf during a nova?

A nova is a surface eruption on a white dwarf that ejects material but leaves the white dwarf intact.

What is the defining outcome of a Type Ia supernova?

A Type Ia supernova is a thermonuclear explosion that destroys a white dwarf in a binary system.

Why can an iron-rich stellar core collapse?

Iron fusion does not release energy to support the core, so an iron-rich core in a sufficiently massive star can collapse rapidly.

What makes a neutron star extraordinarily dense?

A neutron star packs more mass than the Sun into a sphere about 20 kilometers across, made mostly of neutron-rich matter.

What produces the repeating signals of a pulsar?

A pulsar is a rotating neutron star whose beams of radiation sweep across Earth like a lighthouse.

What defines a black hole's event horizon?

A black hole is so compact that nothing, not even light, can escape from inside its event horizon.

How can astronomers detect a stellar-mass black hole indirectly?

Astronomers infer stellar-mass black holes from gravitational effects, such as a companion star's motion, or from radiation emitted by hot gas in an accretion disk.

What happens in a core-collapse supernova?

A core-collapse supernova follows the collapse of a massive star's core, expelling outer layers; the remnant may be a neutron star or black hole.

How does fusion build elements inside massive stars?

During a massive star's life, fusion builds elements from lighter nuclei through the iron group.

Where does the s-process build some heavy elements?

The slow neutron-capture process, or s-process, builds some heavy elements in evolved stars.