A team of scientists led by Dr Roger Deane from the University of Cape Town in South Africa has discovered a system of three supermassive black holes – with two of them orbiting each other rather like binary stars – in a galaxy more than 4 billion light-years away from Earth. The discovery could help astronomers in the search for gravitational waves (the ripples in space-time) predicted by Albert Einstein.
“Einstein’s General Relativity predicts that merging black holes are sources of gravitational waves and in this work we have managed to spot three black holes packed about as tightly together as they could be before spiraling into each other and merging,” said Prof Matt Jarvis from the University of Oxford, who is a co-author of the discovery paper published in the journal Nature.
“The idea that we might be able to find more of these potential sources of gravitational waves is very encouraging as knowing where such signals should originate will help us try to detect these ripples in space-time as they warp the Universe.”
In their study, Dr Deane, Prof Jarvis and co-authors examined six galaxies thought to contain binary supermassive black hole systems.
The astronomers found that one of these galaxies, SDSS J150243.09+1111557.3 (J1502 for short), they thought contained two black holes (J1502P and J1502S) actually contained a triple system with a very compact double supermassive black hole.
They then used the European Very Long Baseline Interferometry Network and the 305-m Arecibo Observatory in Puerto Rico to observe the inner two black holes, J1502SE and J1502SW.
“Very little is actually known about black hole systems that are so close to one another that they emit detectable gravitational waves,” the scientists said.
“This discovery not only suggests that close-pair black hole systems emitting at radio wavelengths are much more common than previously expected,” Prof Jarvis said.
“This exciting discovery perfectly illustrates the power of the Very Long Baseline Interferometry technique, whose exquisite sharpness of view allows us to see deep into the hearts of distant galaxies,” said co-author Dr Keith Grainge from the University of Manchester.
R.P.Deane et al. A close-pair binary in a distant triple supermassive black hole system. Nature, published online June 25, 2014; doi: 10.1038/nature13454