There’s a supermassive black hole – 4 million times our sun’s mass – in the center of our Milky Way galaxy. Astronomers who’ve measured star movements near this central black hole are now saying there might be a 2nd companion black hole near it.
We know of a couple of dozen so-called “stellar-mass” black holes in our Milky Way galaxy. They tend to be between about 5 and 20 times as heavy as our sun. This new black hole – in a distant spiral arm of the galaxy – is 70 times as heavy as the sun.