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Sagittarius A*

This article is about the black hole. For the surrounding region, see Sagittarius A.

Sagittarius A*

Sagittarius A* imaged by the Event Horizon Telescope in 2017, released in 2022
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 17h 45m 40.0409s
Declination −29° 0′ 28.118″[1]
Details
Mass8.54×1036 kg
4.297×106[2] M☉
Astrometry
Distance26996±33[2] ly
(8277±9[2] pc)
Database references
SIMBADdata

Sagittarius A*, abbreviated as Sgr A* (/ˈsædʒ ˈeɪ stɑːr/ SADGE-AY-star[3]), is the supermassive black hole[4][5][6] at the Galactic Center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic,[7] visually close to the Butterfly Cluster (M6) and Lambda Scorpii. Sagittarius A* is a bright and very compact astronomical radio source.

In May 2022, astronomers released the first image of the accretion disk around the event horizon of Sagittarius A*,[8] using the Event Horizon Telescope, a world-wide network of radio observatories.[9] This is the second confirmed image of a black hole, after Messier 87's supermassive black hole in 2019.[10][11] The black hole itself is not seen; as light is incapable of escaping the immense gravitational force of a black hole, only nearby objects whose behavior is influenced by the black hole can be observed. The observed radio and infrared energy emanates from gas and dust heated to millions of degrees while falling into the black hole.[12]

Sgr A* was discovered in 1974 by Bruce Balick and Robert L. Brown,[13][14] and the asterisk * was assigned in 1982 by Brown,[15] who understood that the strongest radio emission from the center of the galaxy appeared to be due to a compact non-thermal radio object embedded in a larger, and much brighter, radio source, Sagittarius A (Sgr A).

The observation of several stars orbiting Sagittarius A*, particularly star S2, have been used to determine the mass and upper limits on the radius of the object. Based on the mass and the precise radius limits obtained, astronomers concluded that Sagittarius A* was the central supermassive black hole of the Milky Way galaxy.[16] The current best estimate of its mass is 4.297±0.012 million solar masses.[2]

Reinhard Genzel and Andrea Ghez were awarded the 2020 Nobel Prize in Physics for their discovery that Sagittarius A* is a supermassive compact object, for which a black hole was the only explanation.[17]

  1. ^ Reid and Brunthaler 2004
  2. ^ a b c d The GRAVITY collaboration (September 2023). "Polarimetry and astrometry of NIR flares as event horizon scale, dynamical probes for the mass of Sgr A*". Astronomy & Astrophysics. 677: L10. arXiv:2307.11821. Bibcode:2023A&A...677L..10G. doi:10.1051/0004-6361/202347416.
  3. ^ "Astronomers reveal first image of the black hole at the heart of our galaxy". Event Horizon Telescope. May 12, 2022. Archived from the original on May 12, 2022. Retrieved May 12, 2022.
  4. ^ Parsons, Jeff (October 31, 2018). "Scientists find proof a supermassive black hole is lurking at the centre of the Milky Way". Metro. Archived from the original on October 31, 2018. Retrieved October 31, 2018.
  5. ^ Mosher, Dave (October 31, 2018). "A 'mind-boggling' telescope observation has revealed the point of no return for our galaxy's monster black hole". The Middletown Press. Business Insider. Archived from the original on October 31, 2018. Retrieved May 16, 2022.
  6. ^ Plait, Phil (November 7, 2018). "Astronomers See Material Orbiting a Black Hole *Right* at the Edge of Forever". Bad Astronomy. Syfy Wire. Archived from the original on November 10, 2018. Retrieved November 12, 2018.
  7. ^ Calculated using Equatorial and Ecliptic Coordinates Archived July 21, 2019, at the Wayback Machine calculator
  8. ^ Sutter, Paul (May 20, 2022). "How did astronomers take a picture of our galaxy's supermassive black hole?". Astronomy Magazine. Retrieved April 16, 2025. The Event Horizon Telescope (EHT) collaboration released the first ever image of the accretion disk around the Milky Way's supermassive black hole, Sagittarius A* (Sgr A*), on May 12, 2022.{{cite web}}: CS1 maint: url-status (link)
  9. ^ Bower, Geoffrey C. (May 2022). "Focus on First Sgr A* Results from the Event Horizon Telescope". The Astrophysical Journal. Archived from the original on July 19, 2022. Retrieved May 12, 2022.
  10. ^ "Astronomers reveal first image of the black hole at the heart of our galaxy". eso.org. May 12, 2022. Archived from the original on May 12, 2022. Retrieved May 12, 2022.
  11. ^ Cite error: The named reference NYT-20220512 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference DetectionOfBlackHoleSrgA was invoked but never defined (see the help page).
  13. ^ Balick, B.; Brown, R. L. (December 1, 1974). "Intense sub-arcsecond structure in the galactic center". Astrophysical Journal. 194 (1): 265–270. Bibcode:1974ApJ...194..265B. doi:10.1086/153242. S2CID 121802758.
  14. ^ Melia 2007, p. 7
  15. ^ Brown, Robert L. (November 1, 1982). "Precessing Jets in Sagittarius A: Gas Dynamics in the Central Parsec of the Galaxy". The Astrophysical Journal. 262: 110–119. Bibcode:1982ApJ...262..110B. doi:10.1086/160401.
  16. ^ Henderson, Mark (December 9, 2009). "Astronomers confirm black hole at the heart of the Milky Way". Times Online. Archived from the original on December 16, 2008. Retrieved June 6, 2019.
  17. ^ "The Nobel Prize in Physics 2020". October 6, 2020. Archived from the original on April 24, 2021. Retrieved October 7, 2020.

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