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Supermassive black hole
Sagittarius A*
The supermassive black hole at the center of our own galaxy — the closest supermassive black hole to Earth, and the first to be directly imaged in 2022.
Estimated mass~4.3 million solar masses
Distance from Earth~26,000 light-years
Event horizon diameter~24 million km (event horizon)
ConstellationSagittarius
DiscoveryRadio source found 1974; confirmed as a black hole via stellar orbits over the following decades
Host galaxyThe Milky Way (our own galaxy)
About Sagittarius A*
Sagittarius A* sits at the exact center of the Milky Way. Its mass was determined with high precision by tracking the orbits of stars swinging closely around it over decades of observation — work that won the 2020 Nobel Prize in Physics. In May 2022, the Event Horizon Telescope collaboration released the first direct image of it: a glowing ring of superheated gas surrounding its dark shadow.
Interesting facts
- Despite its enormous mass, Sagittarius A* is relatively quiet — it isn't actively feeding on large amounts of gas and dust the way many other supermassive black holes are.
- Stars near the galactic center have been observed completing full orbits around it in well under 20 years, moving fast enough to make Sagittarius A*'s gravity unmistakable.
- It took over five years of data processing across a global network of radio telescopes to produce its 2022 image.