Neutron star
A compact stellar remnant formed when a massive star’s core collapses. Its matter is compressed to extreme density and consists mostly of neutrons.
Core-collapse supernova: An explosion caused when the core of a massive star collapses and its outer layers are expelled. This explosion often accompanies the collapse that leaves a neutron star behind.
Neutron: An electrically neutral subatomic particle found in atomic nuclei, composed of three quarks. Neutrons are the dominant constituents of the matter inside these stars.
Lev Landau: A Soviet theoretical physicist whose work spanned condensed matter, quantum theory, and astrophysics. His 1932 writing anticipated exceptionally dense stellar matter shortly after the neutron’s discovery.
Binary neutron star: A gravitationally bound system containing two neutron stars. Its inspiral and merger expose neutron-star masses, tides, and dense-matter behavior.
White dwarf: A compact stellar remnant supported mainly by electron degeneracy pressure. White dwarfs are less dense remnants supported by electrons rather than neutron-rich matter.
Electron capture: A nuclear process in which an atomic nucleus absorbs an electron, converting a proton into a neutron and a neutrino. It reduces pressure-supporting electrons and helps turn a collapsing core neutron-rich.
Nuclear matter: Matter consisting primarily of protons and neutrons interacting through the strong nuclear force. Neutron-star interiors are an extreme, gravitationally compressed state of nuclear matter.
Walter Baade: A German-American astronomer who made major contributions to stellar astronomy and galaxy classification. He and Fritz Zwicky proposed neutron stars as remnants of supernovae in 1934.
Gravitational wave: A ripple in spacetime produced by accelerating masses and propagating outward at the speed of light. Signals from neutron-star mergers reveal their dynamics and constrain their internal matter.
Black hole: A region of spacetime from which nothing, not even light, can escape beyond its event horizon. A neutron star retains a material surface, while a sufficiently massive remnant collapses past an event horizon.