Cosmic lens exposes spin of supermassive black hole

The light coming from matter falling into a black hole 6 billion light-years away was magnified and split into four images by a large galaxy that sits much closer to Earth. This composite image shows the four bright spots (purple) in a ring that gave away the black hole's existence and ultimately its spin.

X-ray: CXC/NASA; Optical: STScI/NASA

By Ashley Yeager

March 6, 2014 at 10:21 am

A chance alignment of a bright, distant galaxy behind a much closer one has given astronomers a rare opportunity to determine the spin of a supermassive black hole 6 billion light-years from Earth.

The alignment of the galaxies, a phenomenon called a gravitational len s, magnified and split the light coming from matter falling into the more distant galaxy’s supermassive black hole. From the four split images, astronomers were able to calculate that the supermassive black hole spins at nearly half the speed of light, which is considered relatively fast.

The new study is the first to measure the spin of a supermassive black hole that is roughly 7 billion years old and the first to suggest that supermassive black holes from this time acquire matter consistently rather than chaotically, the team reports March 5 in Nature.