Intermediate-mass Black Hole
A black hole with a mass between 100 and 100,000 times that of our Sun, filling the gap between stellar-mass and supermassive black holes.
A black hole whose mass falls between stellar-mass black holes (formed from collapsed stars, typically 5–100 solar masses) and supermassive black holes (millions to billions of solar masses found in galaxy centers). With masses ranging from roughly 100 to 100,000 times the Sun's mass, these objects occupy a puzzling middle ground. Their formation mechanism remains debated—they may form from merging stellar black holes, direct collapse of dense star clusters, or leftover seeds from the early universe.
What this means in real life
Astronomers detected gravitational waves from two black holes merging to create a 142-solar-mass object—too heavy to be stellar, too light to be supermassive, fitting squarely in this mysterious middle category.
What it isn’t
Not simply a 'medium-sized' version of the supermassive black holes at galaxy centers. These objects likely form through entirely different processes and exist in different environments, often wandering through galaxies rather than anchoring their cores.
Commonly misused online
Space enthusiasts sometimes call any black hole that isn't Sagittarius A* or a stellar remnant 'intermediate-mass,' but the term has a specific mass range (100–100,000 solar masses) with distinct astrophysical significance.