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Neutron Star ○꠹｜Definition｜1st｜20251119205401-00-⌔
Neutron star
A neutron star is the gravitationally collapsed core of a massive supergiant star. It results from the supernova explosion of a massive star —combined with gravitational collapse —that compresses the core past white dwarf star density to that of atomic nuclei. Surpassed only by black holes, neutron stars are the second-smallest- and second-densest-known class of stellar objects.1 Neutron stars have a radius on the order of 10 kilometers (6 miles) and a mass of about 1.4 solar masses (M).2 Stars that collapse into neutron stars typically have an initial total mass between 10 and 25 M or possibly more for those that are especially rich in elements heavier than hydrogen and helium.3
There are thought to be around one billion neutron stars in the Milky Way,4 and at a minimum several hundred million, a figure obtained by estimating the number of stars that have undergone supernova explosions.5 However, many of them have existed for a long period of time and have cooled down considerably. Originally it was thought that neutron stars would be difficult to detect due to low emissions. However, it was discovered that spinning stars emit radiation. Most neutron stars that have been detected are pulsars or a part of a binary system.
Neutron stars in a binary system with a main sequence star can pull in large amounts of gas from its companion, a process called accretion. These binary systems continue to evolve, with many companions eventually becoming compact objects such as white dwarfs or neutron stars themselves, though other possibilities include a complete destruction of the companion through ablation or collision.
The study of neutron star systems is central to gravitational wave astronomy. The merger of binary neutron stars produces gravitational waves and is associated with kilonovae6 and short gamma-ray bursts.7 In 2017, the LIGO and Virgo interferometer sites observed GW170817, the first direct detection of gravitational waves from such an event.8 Prior to this, indirect evidence for gravitational waves was inferred by studying the gravity radiated from the orbital decay of a different type of (unmerged) binary neutron system, the Hulse–Taylor pulsar.
Printed 2026-06-28.
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Link to original Footnotes
Glendenning, Norman K. (2012). Compact Stars: Nuclear Physics, Particle Physics and General Relativity (illustrated ed.). Springer Science & Business Media. p. 1. ISBN 978-1-4684-0491-3. Archived from the original on 2017-01-31. Retrieved 2016-03-21. ↩
Seeds, Michael; Backman, Dana (2009). Astronomy: The Solar System and Beyond (6th ed.). Cengage Learning. p. 339. ISBN 978-0-495-56203-0. Archived from the original on 2021-02-06. Retrieved 2018-02-22. ↩
Heger, A.; Fryer, C. L.; Woosley, S. E.; Langer, N.; Hartmann, D. H. (2003). “How Massive Single Stars End Their Life”. Astrophysical Journal. 591 (1): 288–300. arXiv:astro-ph/0212469. Bibcode:2003ApJ…591..288H. doi:10.1086/375341. S2CID 59065632. ↩
“NASA.gov”. Archived from the original on 2018-09-08. Retrieved 2020-08-05. ↩
Camenzind, Max (24 February 2007). Compact Objects in Astrophysics: White Dwarfs, Neutron Stars and Black Holes. Springer Science & Business Media. p. 269. Bibcode:2007coaw.book…C. ISBN 978-3-540-49912-1. Archived from the original on 29 April 2021. Retrieved 6 September 2017. ↩
Lea, Robert (21 February 2024). “James Webb Space Telescope finds neutron star mergers forge gold in the cosmos: ‘It was thrilling’”. Space.com. ↩
Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Richard; Howard; Adhikari, R. X.; Huang-Wei (2017). “Multi-messenger Observations of a Binary Neutron Star Merger”. The Astrophysical Journal Letters. 848 (2): L12. arXiv:1710.05833. Bibcode:2017ApJ…848L..12A. doi:10.3847/2041-8213/aa91c9. S2CID 217162243. ↩
Abbott, B. P.; et al. (LIGO Scientific Collaboration & Virgo Collaboration) (16 October 2017). “GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral”. Physical Review Letters. 119 (16) 161101. arXiv:1710.05832. Bibcode:2017PhRvL.119p1101A. doi:10.1103/PhysRevLett.119.161101. PMID 29099225. S2CID 217163611. ↩
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