How many black holes are there?
To use a technical term, gobs. Astronomers have discovered several dozen likely "supermassive" black holes in the cores of fairly nearby galaxies, plus many more in the distant objects known as quasars. They have discovered perhaps a dozen or two likely stellar-mass black holes in the Milky Way galaxy (plus one in a satellite galaxy), and a few possible intermediate-mass black holes in the Milky Way and other galaxies. Yet these don't even qualify as the tip of the iceberg - more like a tiny ice chip. Supermassive black holes may inhabit the cores of all galaxies with central bulges of stars, and thousands of stellar-mass black holes may inhabit the Milky Way, with thousands more in each of billions of other galaxies. One of the goals of black-hole researchers is to find as many as possible so they can estimate how common these objects are.
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