For the first time, a pair of supermassive black holes have been discovered which are currently in orbit around one another.
An international team of scientists using the European Space Agency’s XMM-Newton X-ray observatory have identified a supermassive black hole binary, where two black holes are in an elliptical or circular orbit around the other.
A team led by Dr. Fukun Liu, a Professor of the Department of Astronomy at Peking University in China, spotted a disruption in the galaxy SDSS J120136.02+300305.5 (shortened to J120136). Days later, they were able to follow up their observation with the ESA’s XMM-Newton observatory alongside NASA’s Swift satellite.
The team found that J120136 was emitting X-rays into space at an alarming rate. In active galaxies, black holes feed and consume gas clouds. Their destruction heats the gas to such extremes that they shine in many wavelengths including X-ray.
Scientists speculated that a disruption caused by a supermassive black hole could be occurring in the galaxy so they continued to observe and monitor it. The X-rays began to fade, however on the 27th and 48th day after observation begun, the X-rays increased again. They then continued to fade, as if nothing had happened.
Dr Liu announced, “This is exactly what you would expect from a pair of supermassive black holes orbiting one another.”
It is believed that most massive galaxies harbour a supermassive black hole at their centre. However the identification of two supermassive black holes hints at the rare possibility that two galaxies have merged.
The distance between the orbiting black holes is believed to be relatively small. Scientists understand that they are about 2 thousandths of a light year apart, approximately the width of our Solar System.
Being in such close proximity, the black holes will eventually spiral together. In around two million years, the team believe they will merge into a single black hole.
The identification of two orbiting black holes has huge implications in the scientific community. Not only does it undermine previous theories that such an event could not occur, but it provides a new perspective on how galaxies were first formed.
Their existence can contribute invaluable information on how galaxies have evolved into their present-day shapes and sizes, providing a completely new angle for scientists around the world.
Now that astronomers have identified the first candidate for a binary black hole, the hunt is on for more. Finding pairs of supermassive black holes is an extremely rare phenomenon, but if discovered, they can reveal a wealth of information.
— Rebecca Davies, Correspondent (Science)
Image Courtesy: NASA Goddard Space Flight Center (https://www.flickr.com/photos/24662369@N07/4398655085), Licensed under the Creative Commons Attribution 2.0 Generic | Flickr