Using NASA's Chandra X-ray Observatory, astronomers were able to determine why materials around a giant black hole in the Milky Way had extraordinarily faint x-rays.
Researchers have always wondered why Sagittarius A* (Sgr A*), the location of a giant black hole in the center of the Milky Way, doesn't get any bigger even though it has a mass four million times that of the Sun. Using NASA's Chandra X-ray Observatory, astronomers were able to determine the reason behind this and also why materials around a giant black hole in the Milky Way had extraordinarily faint x-rays.
Sagittarius A* turns out to be a messy eater! According to images obtained, only 1 percent of the gas within the black hole reaches the hole's point of no return, called the event horizon. This means that 99 percent of the gas is spewed back into space and doesn't get the chance to reach the event horizon where it brightens.
"We think most large galaxies have a supermassive black hole at their center, but they are too far away for us to study how matter flows near it," said Q. Daniel Wang of the University of Massachusetts in Amherst in a press release. "Sgr A* is one of very few black holes close enough for us to actually witness this process."
The recent findings were made using data from one of Chandra's longest observation campaigns that lasted for five weeks. During this period, Chandra gathered detailed and sensitive X-ray images and energy signatures of super-heated gas swirling around Sgr A*.
To reach the event horizon, material must lose heat and momentum and for this to happen, other matter must be ejected from the black hole. This is probably the reason why 99 percent of gas is rejected by the black hole.
"Most of the gas must be thrown out so that a small amount can reach the black hole", said Feng Yuan of Shanghai Astronomical Observatory in China, the study's co-author. "Contrary to what some people think, black holes do not actually devour everything that's pulled towards them. Sgr A* is apparently finding much of its food hard to swallow."
Sgr A* is located at a distance of about 26,000 light-years from Earth. The gas it receives is very diffused and super-hot, making it all the more difficult for the black hole to absorb it. Other black holes that produce huge amounts of radiation are known to have gas reservoirs much cooler and denser than that of Sgr A*.
"This new Chandra image is one of the coolest I've ever seen," said co-author Sera Markoff of the University of Amsterdam in the Netherlands. "We're watching Sgr A* capture hot gas ejected by nearby stars, and funnel it in towards its event horizon."
