Scientists from Europe have found two supermassive black holes orbiting around each other. The recent find marks the first time in history that paired supermassive black holes have been observed in a normal galaxy.
Astronomers are no strangers to supermassive black holes. Since they were first theorized back in 1971, scientists have discovered a number of these large black holes. Scientists are also confident that most of the larger galaxies in the universe have supermassive black holes in their galactic centers. Since it is believed that most normal galaxies would only have one such black hole in their cores, the presence of two supermassive black holes makes it extremely likely that a galactic merger occurred in the past.
The find is significant because there are currently only a handful of known galaxies that are suspected of having binary supermassive black holes. The massive gravity wells take in an unimaginable amount of matter and energy. When matter is sucked into a black hole, it causes heat and energy to be emitted. Measuring these emissions, which includes X-rays and a variety of other wavelengths, allow scientists to confirm the existence of black holes.
"There might be a whole population of quiescent galaxies that host binary black holes in their centers," said Max-Planck-Institut für Radioastronomie's Stefanie Komossa. While this scenario may indeed be possible, confirming the existence of these massive binary systems may prove to be difficult. The problem lies in the fact that ordinary galaxies often have dark cores due to the lack of gas clouds in these galactic centers. Without any gas to feed their insatiable appetites, these black holes do not emit energy that can currently be detected on Earth.
The supermassive black holes were found by the European Space Agency's XMM-Newton Space Observatory. The existence of the black hole pair was first hinted by a tidal disruption event found by the ESA space observatory. The event was discovered in a galaxy called SDSS J120136.02+300305.5. Astronomers later checked the data regarding the disruption. They found fluctuations in the amount of x-rays emitted from the galaxy's center. At first, scientists were puzzled by the fluctuations until they realized that the strange modulations were caused by two supermassive black holes orbiting each other.
"This is exactly what you would expect from a pair of supermassive black holes orbiting one another," said Fukun Lui, a professor from Pecking University's Department of Astronomy.
After the discovery was made, scientists will now start looking for similar supermassive black hole pairs in other galaxies by looking for the same type of tidal disruption event observed in the SDSS J120136.02+300305.5 galaxy.
"Once we have detected thousands of tidal disruption events, we can begin to extract reliable statistics about the rate at which galaxies merge," said Komossa.
