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A0620-00 ❍｜Definition｜1st｜20251119205401-00-⌔
A0620-00
A0620-00 (abbreviated from 1A 0620-00) is a binary star system in the constellation of Monoceros, with an apparent magnitude of 11.2.
A0620-00 consists of two objects. The first object is a K-type main-sequence star.[^5][^6] The second object cannot be seen, but based on its calculated mass of about 6 M,[^8][^5] it is too massive to be a neutron star and must therefore be a stellar-mass black hole. The two objects orbit each other every 7.75 hours. At a distance of roughly 3,300 light-years (1,000 parsecs) away, the black hole of A0620-00 would be one of the nearest known black holes to the Solar System, closer than GRO J1655-40.1
A0620-00 has undergone two X-ray outbreaks. The first one was in 1917.2 The second burst, in 1975, was detected by the Ariel 5 satellite.3 During that time, A0620-00 was the brightest X-ray point source. It is now classified as an X-ray nova. Its black hole nature was determined in 1986.
The black hole in A0620-00 pulls matter from the K-type star into an accretion disk.[^5] The accretion disk emits significant amounts of visible light and X-rays. Because the K-type star has been pulled into an ellipsoidal shape, the amount of surface area visible, and thus the apparent brightness, changes from the Earth’s perspective. A0620-00 also bears the variable star designation V616 Monocerotis.[
Printed 2026-06-28.
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Foellmi, Cédric (2009). “What is the closest black hole to the Sun?”. New Astronomy. 14 (8): 674–691. arXiv:0812.4232. Bibcode:2009NewA…14..674F. doi:10.1016/j.newast.2009.04.003. S2CID 12843219. ↩
Eachus, L. J.; Wright, E. L.; Liller, W. (1976). “Optical observations of the recurrent nova associated with A0620-00 - 1917-1975”. Astrophysical Journal. 203: L17–L19. Bibcode:1976ApJ…203L..17E. doi:10.1086/182009. ↩
Elvis, M.; Page, C. G.; Pounds, K. A.; Ricketts, M. J.; Turner, M. J. L. (1975). “Discovery of powerful transient X-ray source A0620-00 with Ariel V Sky Survey Experiment”. Nature. 257 (5528): 656–657. Bibcode:1975Natur.257..656E. doi:10.1038/257656a0. S2CID 4160399. ↩
A0620-00 ❍｜SIMBAD｜1st｜20251021001049-00-●
1A 0620-00
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