Astronomers have discovered three supermassive black holes at the heart of a single galaxy.
Thanks to the Muse instrument equipping the Very Large Telescope based in Chile, an international team of astronomers has just discovered a celestial object with unique characteristics: a galaxy having at its center, not one, but three supermassive black holes.
Called NGC 6240, it is about 400 million light years from Earth in the direction of the constellation Ophiuchus. With its unusual shape reminiscent of a butterfly or a lobster, extremely luminous in the infrared domain, this galaxy had already been talked about just ten years ago, when the Chandra space telescope revealed that 'it contained two supermassive black holes. Today, Muse's extreme sensitivity allows us to detect one more.
Cosmic pocket square
As for these black holes, they are not only three, but they are also colossal. Conventionally, the black holes that inhabit the heart of galaxies are at least a million times more massive than the Sun. This is, for example, the case of Sagittarius A * which is in the center of our Milky Way and which weighs about 4 million solar masses. Nothing compares to the central black holes of NGC 6240 which each have a mass equivalent to no less than 90 million Sun!
How could something so big have escaped astronomers so far? Besides the fact that seeing a black hole which, by definition, emits no light by itself is far from easy, it is also that these three black holes are, on an astronomical scale, practically glued to each other. other. They fit in a cosmic pocket handkerchief of only 3,000 light years!
Merger of three galaxies
Besides the curiosity that such a formation can arouse, never seen before in the Universe, its existence sheds light on one of the fundamental questions in astronomy. How could galaxies as large as those we observe today have formed in just 13.8 billion years (since it is the age of the Universe)? In fact, if NGC 6240 has three black holes, it is actually the result of the fusion of three smaller galaxies. Each of the central black holes of the latter having finally found itself in the center of the whole.
This confirms one of the scenarios proposed to explain the accelerated growth of certain galaxies: they would have grown by the simultaneous fusion of three galaxies and why not more! It is a first step. To be convinced, it would now be necessary to find other objects of the same type in order to prove that NGC 6240 is not just an isolated case.
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