Astronomers usually believe that black holes, very dense space objects whose gravity is so great that even light cannot escape, are created by the powerful explosion of a large dying star, that is, a supernova. However, some may be born in a different way.
Scientists have identified a black hole that appears to have been created by the collapse of the core of a large, dying star, but without the usual explosion.
It was observed to be gravitationally bound to two ordinary stars. Astronomers have identified black holes in so-called binary systems with another star or black hole.
But this is the first confirmed example of a triple system of a black hole and two stars. The system is located almost 7800 light years from Earth in the constellation Cygnus. The black hole, named V404 Cygni, has been studied in detail since it was confirmed in 1992. It was previously believed to orbit just one other star, but data from the European Space Agency shows it has two companions.
Scientists said the black hole, estimated to have a mass nine times that of the Sun, is currently devouring a companion, a star seven-tenths the mass of the Sun. The star orbits the black hole every six and a half days at a distance one-seventh of Earth's distance from the Sun.
The black hole absorbs material from that star, which is in the red giant phase. Scientists have discovered another star, whose mass is 1.2 solar masses, which is gravitationally bound to those two objects, but quite far away, orbiting them every 70 thousand years at a distance 3500 times greater than the distance of Earth from the Sun.
The reason why scientists believe that the black hole was formed by a gentle process is simple. The triple system will collapse if the star that became a black hole explodes.
Scientists have estimated that the members of that triple system formed about 4 billion years ago as ordinary stars. That system may not have three members forever as the black hole is devouring its nearest neighbor.
"People have actually predicted that black hole binaries could arise from triple systems, but until now there was no direct evidence," said astronomer and co-author of the study from Caltech, Karim El-Badri. /Telegraph/
