Intermediate-mass black hole

An intermediate-mass black hole has a mass between those of stellar-mass and supermassive black holes, commonly estimated at roughly 100 to 100,000 solar masses. Its origin and abundance remain uncertain.

Gravitational-wave astronomy: The study of cosmic phenomena through gravitational waves, ripples in spacetime produced by accelerating masses. Mergers involving intermediate-mass black holes can produce gravitational waves detectable by observatories.
Direct-collapse black hole: A black hole formed when a massive gas cloud collapses without first becoming an ordinary star. Direct collapse could create intermediate-mass seeds for later supermassive black holes.
Stellar-mass black hole: A black hole formed through stellar evolution, typically containing several to tens of solar masses. It occupies the lower-mass range and has a well-established population of candidates.
LIGO–Virgo–KAGRA: An international collaboration operating ground-based gravitational-wave detectors. Its detections can test whether mergers create black holes in the intermediate-mass range.
Tidal disruption event: A flare produced when a star is torn apart by a black hole's tidal forces. A distinctive disruption flare can expose a black hole in the intermediate-mass range.
Population III star: A hypothesized first-generation star made almost entirely of hydrogen and helium. The remnants of unusually massive early stars may have seeded intermediate-mass black holes.
Supermassive black hole: A black hole at a galaxy's center with a mass of millions to billions of solar masses. It occupies the upper range and anchors the question of how intermediate-mass objects grow.
Laser Interferometer Space Antenna: A planned space-based gravitational-wave observatory designed to detect low-frequency waves. Its frequency range could reveal massive black-hole mergers inaccessible to ground-based detectors.
Dynamical friction: A drag force on a moving massive object caused by its gravitational interaction with surrounding matter. It governs how quickly a candidate black hole can sink toward a galaxy's center.
Runaway stellar collision: A sequence of stellar mergers in a dense cluster that can produce an exceptionally massive star. The resulting star may collapse into a black hole within the intermediate-mass range.

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