astro final

Solar mass

A unit equal to the mass of the Sun; used to compare masses of stars, remnants, and black holes.

Stellar remnant mass rule of thumb

In the review notes: stars under 10 solar masses become white dwarfs, 10-20 solar masses become neutron stars, and over 20 solar masses become black holes.

White dwarf

The compact remnant expected from a lower-mass star; it is supported against gravity by electron degeneracy pressure.

Neutron star

The compact remnant expected from a more massive collapsed stellar core; it is extremely dense and mostly made of neutrons.

Black hole

A remnant so compact that light cannot escape from inside its event horizon.

Schwarzschild radius

The radius of the event horizon for a non-rotating black hole; it scales directly with mass.

Schwarzschild radius of the Sun

If the Sun became a black hole, its Schwarzschild radius would be about 3 km.

Black hole radius scaling

A 1 solar-mass black hole has a radius of about 3 km, so an X solar-mass black hole has a radius of about 3X km.

Earth as a black hole

If Earth were compressed into a black hole, it would be roughly centimeter-sized according to the review notes.

Neutron star collapse limit

If the leftover neutron star exceeds about 3 solar masses, it will collapse into a black hole.

Pulsar

A rapidly rotating neutron star whose beams of radiation sweep past Earth as regular pulses.

Fastest pulsar in review notes

The review notes list the fastest pulsar as rotating once every about 1.5 milliseconds.

Mass loss during remnant formation

Stars lose a large amount of mass when they transform into white dwarfs, neutron stars, or black holes.

Free neutron decay

Free neutrons spontaneously decay, but conditions inside neutron stars prevent the neutrons from decaying normally.

Black dwarf

A cooled, dark white dwarf; the review notes say a white dwarf may take over 100 trillion years to become one.

Chandrasekhar limit

The approximate 1.4 solar-mass limit for a white dwarf core; exceeding it makes the white dwarf unstable.

White dwarf core at 1.4 solar masses

In the review notes, a white dwarf core of 1.4 solar masses is associated with becoming a neutron star.

Gravitational waves

Ripples in spacetime that can reveal compact-object events such as black hole mergers.

Observing black holes indirectly

Black holes can be detected through effects such as gravitational waves, X-ray emission, or motion of nearby material.

225 solar-mass black hole detection

The review notes mention a black hole of about 225 solar masses detected using gravitational waves.

Maximum single-star black hole mass

In the review notes, the most massive black holes formed from single stars are about 60 solar masses.

Black hole mergers

Mergers can produce black holes larger than those typically formed by single stars.

Intermediate-mass black hole

A black hole between stellar-mass and supermassive scales; the review notes cite about 10^5 solar masses.

X-ray luminosity and black holes

Very high X-ray luminosity can imply the presence of an intermediate-mass black hole.

Type Ia supernova

In the review notes, SN Ia occurs when a white dwarf exceeds its mass limit and explodes.

Type Ia supernova element production

The review notes say SN Ia can produce elements up to uranium.

Type II supernova

A core-collapse supernova that happens when a massive star builds an iron core and can no longer support itself.

Iron core problem

Fusion of iron does not produce outward energy pressure, so the core collapses under gravity.

Type II supernova ejecta

The review notes say SN II expels lighter elements during the explosion.

Core-collapse black hole formation

If a collapsing core exceeds the relevant mass limit, it can continue collapsing into a black hole.

TOV or NOV limit

In the review notes, this is described as a mass limit analogous to the Chandrasekhar limit; exceeding it leads toward black hole formation.

Electron capture

Proton plus electron becomes neutron plus neutrino.

Neutrino

A very low-mass particle produced in processes such as electron capture during core collapse.

Neutrino mass scale

The review notes say a neutrino's mass could be about a billionth of an electron's mass.

Supernova explosion analogy

The review notes compare a supernova explosion to a falling weight hitting mustard and forcing material outward.

SN 1006

A historically observed supernova; the review notes mention a Northern Europe record and a Swiss write-up.

Brightness variation in neutron stars

If an observed neutron star shows no brightness variation, the review notes say that implies no spin.

Nyquist frequency

To observe a frequency correctly, the sampling rate must be at least twice that frequency.

Population I stars

Younger stars located mainly in the galactic disk, in the same plane as the galaxy's center.

Population II stars

Older stars located in a roughly spherical halo or bubble around the galaxy.

Galactic disk

The flattened plane of a galaxy where younger Population I stars are commonly found.

Galactic halo

The roughly spherical region around a galaxy where older Population II stars are commonly found.

Crab pulsar light curve

The Crab pulsar has a repeating brightness signal, or light curve, caused by its rapid rotation.

Little Green Men nickname

Early pulsar signals seemed so regular that they were jokingly linked to "Little Green Men" before neutron stars explained them.

Accretion

The buildup of material onto a compact object; it can release a large amount of energy.

Accretion power

Accretion can produce a lot of power compared with nuclear fusion.

Gravitational radiation

Energy carried away by gravitational waves.

Binary neutron star orbital decay

When two neutron stars orbit, gravitational radiation removes energy, causing the orbit to shrink and the stars to speed up.

Black hole surface

Black holes do not have a solid surface; the meaningful boundary is the event horizon.

Spaghettification

The stretching and squeezing caused by strong tidal forces when falling into a black hole.