A breakthrough has been made as scientists discover a tiny star in a binary system located around 14,800 light years away. The globular cluster is known as 47 Tucanae and is the first of its kind that we know about to consist of a white dwarf that circles the black hole every 28 minutes. It’s the closest orbit that’s ever been observed by scientists in an any black hole and star pair.
Arash Bahramian of the University of Alberta, Canada and Michigan State University, USA, said, “We suspect they’ve been like this for millions or billions of years. And our current understanding is that the system is stable. It can probably stay this way for million of years more.” The white dwarf may not be in any danger of being dragged into the black hole or being ripped apart by it, but it’s still fuelling its partner with a steady stream of space dust and gas. This has never been observed before, where a black hole is feeding off a star and is very exciting for astronomers.
“Although we expect a lot of these systems in globular clusters, we have found a surprisingly low number of them. Until a couple of years ago, this number was zero. We thought perhaps that there were none left to see today – that perhaps black holes gained a lot of speed because of interactions with clusters ad got kicked out, that they left the clusters rapidly after forming, But then evidence suggested some should have survived until today,” says Bahramian.
It’s only been in the past decade or so that astronomers have started to discover these systems, are there’s still only ever been a handful found, including this one. Moving forward, scientists will be able to use these to try and understand the evolution of black holes, globular clusters, and stars. Observatories that detect gravitational waves could be used to learn more about these systems too, but at the moment, none are quite powerful enough. Astronomers are hoping that the new wave observatories planned for the future, should be able to do the job, so I guess we’ll just have to sit tight for now and work with what we have.
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