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

Scientists have found the strongest evidence yet that a black hole and a neutron star collided while moving along an oval shaped orbit instead of the near perfect circles scientists usually expect before such mergers.

From Science Daily • Mar. 12, 2026

In this scenario, the collapse of the star forms a neutron star, an incredibly dense remnant that injects energy into the surrounding debris and boosts the supernova's brightness.

From Science Daily • Mar. 11, 2026

For the most spectacular sequence, with the heroes perilously near a neutron star, the filmmakers checked in with astrophysicist Cliff Johnson weekly.

From Los Angeles Times • Dec. 9, 2025

The neutron star system produces an unusually dense outflow that challenges current ideas about how these winds form and how they reshape their surroundings.

From Science Daily • Nov. 10, 2025

The neutron star at the center of the Crab Nebula is an immense atomic nucleus, about the size of Manhattan, spinning thirty times a second.

From "Cosmos" by Carl Sagan