Why are there giant black holes at the centers of many galaxies?
Quick Answer
Supermassive black holes likely grew over billions of years by swallowing gas, stars, and smaller black holes. Many galaxies also grew through mergers, which helped feed and enlarge their central black holes.
The Full Story
Most large galaxies seem to host a supermassive black hole in their core, including the Milky Way’s Sagittarius A*, which is about 4 million times the mass of the Sun. These black holes likely formed from smaller seeds in the early universe and grew by accreting matter over time. Galaxy mergers can funnel gas toward the center, making the black hole grow even faster. In some galaxies, the black hole powers an active galactic nucleus or quasar, which can outshine the rest of the galaxy. Astronomers think black hole growth and galaxy growth are linked through feedback and repeated mergers.
Key Facts
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"How did galaxies end up with monsters in their centers?"