Talk about orbital science! While astronauts worked inside the International Space Station some 250 miles above our heads, a special science instrument on the station’s outside spotted the signature of a black hole, nicknamed J1820.
While J1820 was feeding on a star, X-ray light from the black hole flowed across space and into the detector aboard NASA’s Neutron star Interior Composition Explorer (NICER) on the space station. What’s more, astronomers say the X-ray waves formed “light echoes” that bounced off the gas spinning near the black hole. These echoes are intriguing because they show how that region is changing in shape and size.
The find is part of a larger question for scientists to understand how black holes work. Black holes form from the collapse of a super-massive star after it runs out of usable fuel and explodes into a supernova. Since black holes are — as the name suggests — dark, the best way we can see them is when they start pulling in material nearby. This doomed star near J1820 (or if you prefer, the more formal MAXI J1820+070) is a perfect example.
Scientists want to know how the swirling gas near the black hole changes while the black hole picks up material from the companion star. They hope that by watching the black hole morph over a few weeks, they can begin the difficult extrapolations of how black holes evolve over millions of years.
Black Holes, From Tiny to Massive
There’s even more complication to these observations. Black holes come in all sorts of sizes. This one is relatively small — we say “relatively” because it’s about 10 times the mass of the sun, but hey, space is a big place. On the scale of black holes, actually, this is nothing. Supermassive black holes that reside in the centers of galaxies, even our own Milky Way, can be many billion times the sun’s mass. This obviously has an effect on how a galaxy evolves. So if astronomers understand how a little black hole works, perhaps they can better understand how the most massive ones function.
“Previously, these light echoes off the inner accretion disk were only seen in supermassive black holes, which are millions to billions of solar masses and undergo changes slowly. Stellar black holes like J1820 have much lower masses and evolve much faster, so we can see changes play out on human time scales,” said lead author Erin Kara, an astrophysicist at the University of Maryland NASA’s Goddard Space Flight Center, in a statement.
NICER also managed to react quickly when the black hole was discovered by yet another space station instrument, Japan’s Monitor of All-sky X-ray Image (MAXI), on March 11, 2018. The scientists with NICER have also been following changes in the corona — the tiny particles above the gas disk that surrounds the black hole. “Astrophysicists want to better understand how the inner edge of the accretion disk and the corona above it change in size and shape as a black hole accretes material from its companion star,” NASA said in the same statement.