Supermassive black hole

A black hole with hundreds of thousands to billions of solar masses, typically found at the center of a galaxy. Its gravity can shape its surroundings and power exceptionally luminous galactic nuclei.

Accretion disk: A rotating structure of gas and dust spiraling around a massive central object. Gas in a disk can heat and radiate intensely before crossing the black hole’s event horizon.
Black hole: A region of spacetime whose gravity prevents anything inside its event horizon from escaping. Supermassive black holes are the highest-mass members of this class of objects.
Primordial black hole: A hypothetical black hole formed from dense fluctuations in the early universe rather than stellar collapse. Such objects could have supplied initial seeds, but their role in supermassive black-hole formation is unconfirmed.
Sagittarius A*: The compact radio source at the center of the Milky Way, associated with a black hole of about four million solar masses. Stellar orbits around it provide direct evidence for a supermassive black hole in our own galaxy.
M–sigma relation: An observed correlation between a galaxy’s central black-hole mass and the velocity dispersion of its stars. It links central black-hole mass with the properties of the surrounding galactic bulge.
Event horizon: The boundary beyond which escape from a black hole is impossible. It marks the limit at which infalling matter and light cease to affect distant observers.
Solar mass: A unit of mass equal to the mass of the Sun, used widely in astronomy. It provides the scale for expressing the enormous masses of these black holes.
Direct-collapse black hole: A massive black-hole seed proposed to form when a primordial gas cloud collapses without first fragmenting into stars. This pathway could create seeds large enough to grow into early supermassive black holes.
M87*: The supermassive black hole at the center of the galaxy Messier 87, imaged by the Event Horizon Telescope. Its resolved shadow and prominent jet make it a landmark observational case.
Galaxy formation and evolution: The processes by which galaxies assemble, form stars, change structure, and interact over cosmic time. Black-hole feedback is one proposed influence on how galaxies grow and stop forming stars.

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