The well-studied V404 Cygni, an X-ray binary hosting a low-mass black hole, is part of a wide hierarchical triple with a tertiary companion at least 3,500 astronomical units (AU) away from the inner binary, according to MIT astrophysicists.
V404 Cygni is located about 7,800 light-years away in the constellation of Cygnus.
This system first jumped to prominence during a nova explosion more than 80 years ago, in 1938.
It also produced eruption in 1989, which was discovered by the Japanese X-ray satellite Ginga and high-energy instruments on board the Mir space station.
Known as Nova Cygni 1989, the 1989 outburst was crucial in the study of black holes.
Until then, astronomers knew only a handful of objects that they thought could be black holes, and V404 Cygni was one of the most convincing candidates.
V404 Cygni is known to host a central stellar-mass black hole in the act of consuming a small star that’s spiraling in very close to the black hole, every 6.5 days — a configuration similar to most binary systems.
But, according to the new study, a second star is circling the black hole, though at a much greater distance.
“We think most black holes form from violent explosions of stars, but this discovery helps call that into question,” said MIT researcher Kevin Burdge.
“This system is super exciting for black hole evolution, and it also raises questions of whether there are more triples out there.”
Dr. Burdge and colleagues estimate the third companion is orbiting the V404 Cygni black hole every 70,000 years.
That the black hole seems to have a gravitational hold on an object so far away is raising questions about the origins of the black hole itself.
Black holes are thought to form from the violent explosion of a dying star — a process known as a supernova, by which a star releases a huge amount of energy and light in a final burst before collapsing into an invisible black hole.
The team’s discovery, however, suggests that if the…
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