ScienceShot: Weighing a Star-Eating Black Hole

Last year, at the center of a galaxy far, far away, astronomers watched a star send out a distress flare when a giant black hole tore it to shreds (artist's conception shown). The flare's name, Swift J1644+57, honors the satellite that spotted it and gives the galaxy's celestial coordinates in the constellation Draco. Now, as researchers report online today in Science, some of the deceased star's glowing remains, which whirl around the black hole and emit x-rays, have revealed the murderer's mass. Two other satellites discovered that the x-rays fluctuate in strength every 200 seconds. Assuming this is the orbital period of hot gas revolving near the black hole, the astronomers deduce that the monster weighs 450,000 to 5 million times more than the sun, agreeing with previous estimates and making the black hole comparable to the 4-million-solar-mass one at the Milky Way's center—but located in a galaxy 3.9 billion light-years away.

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