Image: © Ulia Koltyrina /Stock.adobe.com
The team at MIT and Caltech also discovered that the black hole system is 4bn years old.
In a chance discovery, MIT and Caltech scientists have found two objects orbiting a black hole for the first time, leading them to question what they know about how black holes form.
Black holes, scientists generally find, appear as part of a pair – usually a star, a much denser neutron star or another black hole, that spiral each other, drawn together by the black hole’s gravity, forming a tight pair.
Black holes are thought to form from a violent explosion of a dying star – a process known as a supernova. The explosion would generally push away any loosely bound objects.
However, contrary to this widely held belief, MIT scientists recently discovered this “black hole triple” – a system that contains a central black hole in the act of consuming a small star spiralling extremely close to the black hole, orbiting it once every 6.5 days as well as a secondary star circling the black hole, orbiting it every 70,000 years.
The team of scientists, who have published their findings in Nature, suspect that the black hole formed through a more gentle process of a “direct collapse”, in which a star caves in on itself, forming a black hole without the dramatic flash.
“We think most black holes form from violent explosions of stars, but this discovery helps call that into question,” said study co-author Kevin Burdge, a Pappalardo fellow in the MIT Department of Physics.
“This system is super exciting for black hole evolution, and it also raises questions of whether there are more triples out there.”
Burdge made the discovery when reviewing an image of V404 Cygni, of the first objects to be confirmed as a black hole. Burdge noted two blobs of light – one, the black hole and a closely orbiting star, the second, Burdge determined was most likely coming from a very far-off star – something others had not reported.
Burdge conducted simulations to understand how a triple pair system could have occurred, and he found that the easiest way to make this triple work is through direct collapse.
“We’ve never been able to do this before for an old black hole,” Burdge said. “Now we know V404 Cygni is part of a triple, it could have formed from direct collapse, and it formed about 4 billion years ago, thanks to this discovery.”
In another surprising discovery, earlier this year, scientists spotted what appears to be a massive black hole “awakening in real time”.
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