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Holm 15A*
Details
Holm 15A* is the ultramassive black hole in the central galaxy of the Abell 85 galaxy cluster, measured at about 40 billion solar masses. That makes its event horizon enormous, while Holm 15A’s unusually diffuse center preserves evidence of the mergers that helped build it.
Holm 15A* matters because it is not just a large black hole in isolation. It sits inside Holm 15A, the brightest cluster galaxy of Abell 85, at the center of a dense galactic environment where repeated mergers can build extreme stellar cores and extreme central black holes together.
The central black hole is especially important because its mass was inferred through dynamical modeling of stellar motions, not only from a broad scaling relation. Using VLT/MUSE observations, astronomers found a black hole of about forty billion solar masses in Holm 15A’s core. For a non-rotating black hole, that mass implies an event horizon hundreds of billions of kilometers across.
That makes Holm 15A* a useful bridge between familiar supermassive black holes such as M87* and the more uncertain far end of the scale. It shows how the largest cluster galaxies can turn merger history into a depleted central core, and how the black hole at the middle can become part of the visible structure of the galaxy around it.
103billion km
Visual creditscaleofspace.org / CC BY-NC 4.0
Key facts
- Category
- Black holes
- Object class
- Ultramassive black hole
- Host
- Holm 15A, Abell 85
- Scale fact
- 236 billion kmevent horizon diameter
- Mass
- ~40 billion solar masses
Scale context
Where Holm 15A* sits on the full axis
Together, these objects make the size change around Holm 15A* easy to compare at a glance.
Sources
References for Holm 15A*
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
- Holm 15A* — Wikipedia
- Visual: scaleofspace.org / CC BY-NC 4.0
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