14th March, 2017
Astronomers at Curtin University in Western Australia and the International Center for Radio Astronomy Research have discovered a star with the closest orbit to a black hole ever seen in our galaxy.
The Co-author from Curtin University, Vlad Tudor said on Tuesday that it was located in the globular cluster 47 Tucanae, 14,800 light years away from earth in the Milky Way.
According to him, the system named X9 fluctuates in brightness every 28 minutes, suggesting to scientists a star orbits a stellar companion which is most likely a black hole.
Although the binary couple has been known for decades, it is now believed the large amount of oxygen in the system supports the theory that the star is a white dwarf orbiting a black hole at a distance just 2.5 times, the earth from the moon.
“We actually don’t think it’s that rare.
“What we think is it’s just hard to see them because they’re very faint to observe.
“But with radio telescopes we’ve just got to the level of technology where it’s possible to observe the jets from these systems,’’ Tudor said.
A possible explanation as to why the star is so close is that a red giant and a black hole collided causing gas from the star to eject.
It is by also creating a binary between the newly formed white dwarf star and the black hole.
First author from the University of Alberta in Canada and Michigan State University in the U.S., Arash Bahramian said the process would shrink the orbit of the binary with gravitational waves emitted, causing the black hole to pull in material from the white dwarf.
“This white dwarf is so close to the black hole that material is being pulled away from the star and dumped onto a disk of matter around the black hole before falling in.
“Luckily for this star, we don’t think it will follow this path into oblivion, it should stay in orbit,’’ Bahramian said.