Star survives an encounter with a black hole (for now)

Hyperaxion Apr 28, 2020

The outer layers of the red giant were “sucked” into the black hole, but the star’s core managed to survive and turned into a white dwarf.

The Chandra X-ray Observatory, launched by NASA in 1999, detected an impressive astronomical event, according to an article published in the Monthly Notices of the Royal Astronomical Society. A giant red star narrowly escaped from being eaten by a supermassive black hole.

Star survives an encounter with a black hole (for now)
(Credit: NASA/CXC).

This astronomical encounter took place in the galaxy GSN 069, located 250 million light-years from Earth. According to the scientists, when the red giant was captured by the black hole’s gravity, which is 400,000 times the mass of the Sun, the star’s outer hydrogen layers were “sucked” into the black hole.

The star’s core survived and now has the size and characteristics of a white dwarf star. “In my interpretation of the X-ray data the white dwarf survived, but it did not escape,” said Andrew King, who conducted the study, in a statement. “It is now caught in an elliptical orbit around the black hole, making one trip around about once every nine hours.”

The star continues to lose mass as it orbits the black hole, but at an increasingly slower pace.
The star continues to lose mass as it orbits the black hole, but at an increasingly slower pace. (Credit: NASA/CXC).

The scientist believes that the combined effect of the gravitational waves generated by the encounter and changes in the size of the star should cause the orbit of the white dwarf to become more circular and grow in size. Meanwhile, the star continues losing mass to the black hole, but at an increasingly slower pace.

“It will try hard to get away, but there is no escape. The black hole will eat it more and more slowly, but never stop,” said King. “In principle, this loss of mass would continue until and even after the white dwarf dwindled down to the mass of Jupiter, in about a trillion years. This would be a remarkably slow and convoluted way for the universe to make a planet!”

Events like this are probably more common than direct collisions between stars and black holes. However, astronomers believe that events like the one observed by Chandra are more difficult to detect and end “quickly”, in just 2,000 years. “Such encounters could be one of the main ways for black holes the size of the one in GSN 069 to grow,” said the scientist.

Related topics:

black hole Stars White dwarf

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