BULLETIN

Giant black hole is slower than its peers

The largest black hole to ever have its spin measured is turning slower than its smaller siblings, a new study reveals.

“Every black hole can be defined by just two numbers: its spin and its mass,” says Julia Sisk-Reynes from the University of Cambridge, who led the new research. “While that sounds fairly simple, figuring those values out for most black holes has proved incredibly difficult.”

The black hole at the heart of quasar H1821+643 in the constellation Draco is a colossal 30 billion solar masses, around 10,000 times more massive than the Milky Way’s central black hole. Astronomers measured its spin by looking at X-rays bouncing off the material surrounding it, and found its rotation to be about half the speed of black holes between one and 10 solar masses. It’s thought that these monsters grow by merging together, which disrupts their rotation, slowing them down. The more they grow, the more they slow.

“The moderate spin for this ultra-massive object may be a testament to the violent, chaotic history of the Universe’s biggest black holes,” says co-author James Matthews. www.ast.cam.ac.uk

PICTURE CREDIT: X-RAY: NASA/CXC/UNIV. OF CAMBRIDGE/J. SISK-REYNÉS ET AL/ RADIO: NSF/NRAO/VLA OPTICAL: PANSTARRS