Science
21 times the Sun’s mass: heaviest stellar black hole in the Milky Way is more massive than we thought – The Conversation AU
The black hole is part of a binary star system within our Milky Way galaxy. It orbits a colossal supergiant companion star.

When one of us (Ilya Mandel) started grad school at the California Institute of Technology 20 years ago, he was greeted with a series of bets hanging on the wall outside the office of his PhD advisor, Kip Thorne.
One bet from 1974 was a wager with theoretical physicist Stephen Hawking, on whether an observed galactic X-ray source known as Cygnus X-1 was actually a black hole feeding on hot gas.
Hawking bet it wasnt, as a consolation prize in case black holes turned out not to exist (since this…
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