neutron star

American  

noun

1. an extremely dense, compact star composed primarily of neutrons, especially the collapsed core of a supernova.

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neutron star British  

noun

1. a star that has collapsed under its own gravity to a diameter of about 10 to 15 km. It is composed mostly of neutrons, has a mass of between 1.4 and about 3 times that of the sun, and a density in excess of 10 ¹⁷ kilograms per cubic metre

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neutron star Scientific  

1. A celestial object consisting of an extremely dense mass of neutrons, formed at the core of a supernova, where electrons and nuclei are compressed together so intensely by the force of gravity that protons and electrons merge together into neutrons. Though their mass is close to that of the Sun, the density of neutron stars is much higher—about 3 × 10 ¹¹ kilograms per cubic centimeter (by comparison, the density of steel is 7.7 grams per cubic centimeter). Neutron stars are typically about 10 km across, and rotate very rapidly. Due to the spinning of electrically charged protons and electrons at their surfaces, their rotation gives rise to strong magnetic fields. The existence of neutron stars was predicted in the 1930s but was not confirmed until the discovery of the first pulsar in 1967.

2. See more at pulsar

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neutron star Cultural  

1. A star about the size of the Earth, made almost entirely of neutrons. It is the end product of the evolution of some stars larger than the sun.

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Etymology

Origin of neutron star

First recorded in 1930–35

Example Sentences

Researchers expect it to be about 10 times more sensitive than LIGO, allowing it to detect black hole and neutron star mergers stretching back to the era when the first stars formed.

From Science Daily • Jul. 3, 2026

Depending on conditions, the collapse can leave behind either a neutron star or a black hole.

From Science Daily • May 27, 2026

When a massive object such as a neutron star passes in front of a more distant star, its gravity bends and magnifies the background star's light.

From Science Daily • May 15, 2026

Farah proposed that the supernova left behind a magnetar, a type of neutron star that spins extremely rapidly and has an extraordinarily powerful magnetic field.

From Science Daily • Mar. 11, 2026

One thing he failed to see was that if a neutron star shrank enough it would become so dense that even light couldn’t escape its immense gravitational pull.

From "A Short History of Nearly Everything" by Bill Bryson