When black holes swallow down a lot of material from the area around them, they are not narrow at all. They emit intense flames of X-rays, generated by the material heating to an intense temperature as it is drawn towards the black hole, as clearly as we can detect them. from Earth.
This is the normal behavior of a black hole. What is unusual for these X-ray flames to spew out with clockwork consistency is a chaotic behavior reported in 2019 from a horrible black hole at the center of a 250-million-light-year galaxy. away. Every nine hours, vigor – X-ray flare.
After careful study, astronomer Andrew King of the University of Leicester in the UK identified a possible cause – a dead star that suffered his brush with a black hole, locked in an elliptical orbit nine hours ago. Every close pass, or periastron, the black hole pulls up more of the star’s material.
“This white dwarf is trapped in an elliptical orbit near the black hole, going around every nine hours,” King explained back in April 2020.
“At its closest, about 15 times the radius of the black hole’s incident horizon, gas is dragged off the star into a collection disk around the black hole, releasing X-rays, which are the two spacecraft search. “
The black hole is a galaxy nucleus called the GSN 069, and it is very light as far as black galaxy holes go – just 400,000 times larger than the mass of the sun. Nonetheless, it is active, surrounded by a hot disk of breeding material, feeding in and becoming the black hole.
According to King ‘s model, this black hole was just hanging out, making its collection object active, when a red giant star occurred – the last evolutionary stages of a Sun – like star. – wading a little too close.
The black hole quickly sent the star of the outer layers, accelerating evolution to a white dwarf, the dead heart that remains once the star has released its nuclear fuel (dwarfs white shining with residual heat, not the fusion processes of the living stars).
But instead of continuing on his journey, the white dwarf was caught in orbit around the black hole, and continued to feed into it.
Based on the size of the X-ray flames, and our understanding of the flames emitted by a black hole’s mass, and the orbit of the star, King was able to suppress the mass of the star as well. He found that the white dwarf is about 0.21 times the mass of the sun.
As long as they are on the lighter end of the scale, that is a very normal decoration for a white dwarf. And if we assume that the star is a white dwarf, we can also prove – based on our understanding of other white dwarfs and stellar evolution – that the star is full of helium, long ago run out of hydrogen.
“It’s amazing to think that the orbit, mass and combination of a tiny star 250 million light-years away could be discovered,” King said.
Based on these parameters, he also predicted that the orbit of the star will move slightly, as a spinning top loses speed. This wobble should be repeated every two days or so, and we may be able to detect it, if we look at the system long enough.
This could be one way in which black holes grow more and more over time. But we need to study more such systems to prove it, and they may not be easy to find.
For one, the GSN 069 has a black hole at a lower mass, which means that the star can travel on a closer orbit. To survive in a larger black hole, a star would have to be in a much larger orbit, which means that it would be easier to lose any timeliness in the feeding. And if the star strayed too close, the black hole would destroy it.
But the fact that one has been identified offers hope that this is not the only such system out there.
“In terms of astronomy, this event can only be seen with our conventional telescopes for a short time – around 2,000 years, so if we weren’t very lucky enough to have captured this one, there would probably be a lot of more we are losing elsewhere in the Universe, “King said.
As for the future of the star, well, if nothing else is about to change, the star will stay right where it is, orbit the black hole, and continue to get away to slow for billions of years. This will cause it to grow in size and decrease in density – a white dwarf is only slightly larger than Earth – until it descends to a planetary mass, possibly even turning into a gas giant.
“He will try hard to get away, but there is no escape,” King said. “The black hole will eat it more and more slowly, but it will never stop.”
The research was published in the Monthly notices from the Royal Astronomical Society.
A draft of this article was first published in April 2020.