AsianScientist (Nov. 15, 2016) – As though one supermassive black hole was not impressive enough, the nearby giant spiral galaxy NGC 5252 has recently been found to boast of two. The radio astronomers from China and Europe who made this discovery have published their findings in The Monthly Notices Letters of the Royal Astronomical Society.
It is believed that at the nucleus of every galaxy is a supermassive black hole, a black hole at least a million times larger than the Sun. Since there are many galaxy clusters and interacting galaxies in the Universe, galaxies with two or more supermassive black holes should be ubiquitous as well.
However, it is difficult to find pairs of supermassive black holes that actively accrete mass and have a separation of less than the size of their host galaxies (about the distance between the Sun and the center of the Milky Way). Pairs of active galactic nuclei are quite interesting because they may provide clues on the formation and the growth of giant galaxies and monster black holes.
NGC 5252 is about 320 million light years away from the Milky Way. At the center, it has an active galactic nucleus with a supermassive black hole, recognized by its optical, radio and X-ray properties. A second very luminous X-ray source, catalogued as CXO J133815.6+043255, was found in the outskirts of NGC 5252 last year.
This powerful X-ray source appears quite compact in the optical and radio images, similar to the supermassive black hole in the nucleus. To uncover its mysterious nature, an international team led by Dr. Yang Jun from Onsala Space Observatory of Sweden, has made the highest resolution image of its radio counterpart with the observational technique of very long baseline interferometry (VLBI) provided by the European VLBI Network.
“No doubt it has a compact radio jet in the image with a high resolution of a few milli-arcseconds,” said Mr Yang Xiaolong, a PhD student supervised by Dr. Liu Xiang from Xinjiang Astronomical Observatory of China. “Most likely, the jet is associated with a supermassive black hole,” added Liu.
“This is one of the few unique dual radio-emitting supermassive black holes as far as their small separation is concerned,” commented Dr. An Tao, a radio astronomer in Shanghai Astronomical Observatory of China.
It is not clear whether the two black holes in NGC 5252 will finally merge or not. However, finding more supermassive black hole pairs will definitely enable astronomers to run statistical studies of their final fate.
The article can be found at: Yang et al. (2016) NGC 5252: A Pair of Radio-Emitting Active Galactic Nuclei?
Source: Chinese Academy of Sciences; Photo: Shuttersatock.
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