The black hole in the nearby galaxy M87 weighs in at 6.6 billion suns, making it the local universe’s heavyweight champ.
“This is the biggest black hole in the nearby universe,” said astronomer Karl Gebhardt of the University of Texas at Austin in a press conference today here at the American Astronomical Society meeting.
The behemoth’s bulk, plus the fact that it lives just 50 million light-years away, makes M87 the best candidate for future efforts to take a direct image of a black hole’s event horizon for the first time.
“In terms of the largest galaxies, it really is in our backyard,” Gebhardt said. “Being so close to such a massive black hole allows us a remarkable chance to study what happens around a black hole.”
At nearly 6 trillion times the mass of the sun, M87 is the most massive galaxy in the Milky Way’s cosmic neighbourhood. Astronomers expected it to host a correspondingly huge black hole, but the most commonly accepted estimates — based on measurements from the Hubble Space Telescope — found the black hole weighed just 3 billion solar masses, give or take a billion.
But although Hubble “has taken the lead in terms of black hole measures, it can’t do the biggest ones,” Gebhardt said.
To pin down the monstrous black hole’s mass, Gebhardt and his colleagues used the Gemini North telescope atop Mauna Kea in Hawaii to measure the speeds of stars zipping past the galactic centre.
Using a technique called adaptive optics, in which astronomers shine a laser on the sky and use that point of light to subtract out the stars’ twinkling, Gebhardt’s team was able to measure the velocities of stars within about 2 light-years of M87’s centre using the Gemini telescope. The scientists also took data with a telescope at the McDonald Observatory in Texas.
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