accretion disk

noun

variants or less commonly accretion disc
plural accretion disks also accretion discs
: a disk of usually gaseous matter surrounding a massive celestial object (such as a black hole) in which the matter gradually spirals in toward and accretes onto the object as a result of gravitational attraction
Evans' team studied a supermassive black hole with jets 800 million light-years away named 3C 33. They never found an expected X-ray pattern … which results from light reflecting off the accretion disk.Bill Andrews
Most other moons are either captured planetesimals, or they formed along with the planet in a common accretion disc.Daniel Herwartz, et al.

Examples of accretion disk in a Sentence

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Typically, about half the star's matter is ejected outward while the remainder forms a glowing accretion disk—a structure made of gas, dust or other material that spirals inwards—around the black hole, briefly illuminating the cosmos in various wavelengths. Thomas Westerholm, MSNBC Newsweek, 25 June 2025 The matter falling around the black hole settles into a flattened cloud of gas and dust called an accretion disk, from which material is fed to the central black hole. Robert Lea, Space.com, 23 June 2025 This could be caused by material rotating away from us in the accretion disk. John Timmer, Ars Technica, 17 June 2024 Meanwhile, a lower mass object, likely a star, is orbiting very close to the black hole and periodically plows through the accretion disk. Keith Cooper, Space.com, 9 May 2025 See All Example Sentences for accretion disk

Word History

First Known Use

1972, in the meaning defined above

Time Traveler
The first known use of accretion disk was in 1972

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Cite this Entry

“Accretion disk.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/accretion%20disk. Accessed 9 Jul. 2025.

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