Back when the universe was half its present age, supermassive black holes were feeding from a steady and plentiful diet of neighboring galaxies, the first measurement of a distant supermassive black hole’s spin shows.
Taking advantage of a naturally occurring zoom lens in space, astronomers analyzed X-rays streaming from near the mouth of a supermassive black hole powering a quasar about 6 billion light years from Earth.
“The ‘lens’ galaxy acts like a natural telescope, magnifying the light from the faraway quasar,” University of Michigan astronomer Rubens Reis explains in a paper published in this week’s Nature.
Analyzing four magnified images created by the lens galaxy -- an elliptical galaxy about 3 billion light years away -- Reis and colleagues found that the quasar’s black hole is spinning at half the speed of light.
The spin rate directly relates to how black holes feed and grow: The steadier the diet, the faster the spin, computer models show. “If the mass accretion was more messy it would suggest that the black hole would have a lower spin,” astronomer Mark Reynolds, also with University of Michigan, told Discovery News.
“What we found in this system is that it’s spinning very rapidly,” Reynolds said, consuming mass equivalent to about one sun per year. Spin rates may evolve over time, reflecting changes in evolution of galaxies.
At some distance, the black holes’ spins might be even higher, approaching light speed, and then slow down to RX J1131’s spin rate.
“If we go back further, maybe they’ll all be maximally spinning because of more mergers and more things happening. Or maybe they’ll be less spinning. We can theoretically produce both scenarios at the moment,” Reynolds said.