A black hole is eating a star faster than scientists thought was possible, and its releasing unusually bright X-ray signals that could help scientists better understand a group of superbright objects in deep space.
The discovery should shed some light on the origin of ultraluminous X-ray sources, and also suggests black holes can grow much faster than previously believed, according to researchers who spoke with Space.com.
Astronomers found sources of bright X-rays in deep space in the late 1970s. For a while it was unclear what these ultraluminous X-ray sources were exactly. Most researchers believed black holes powered these mysterious, with the matter around them giving off light as the black holes ripped apart. They disagreed about what the holes' masses could be.
Most black holes are created during the deaths of giant stars. These black holes weigh around three to 100 times the mass of the sun. There are also supermassive black holes that can be millions to billions the mass of the sun, and found in the centers of galaxies.
Ultraluminous X-ray sources have a brightness in between that of stellar-mass and supermassive black holes, according to the researchers. They suggested that these ultraluminous X-ray sources could involve intermediate-mass black holes that are hundreds to thousands of times the mass of the sun.
Scientists now have identified one ultraluminous X-ray source, which turned out not be an intermediate-mass black hole, but instead an unusually bright stellar-mass black hole no more than 15 times the mass of the sun.
"Black holes with relatively modest masses may find ways to radiate huge X-ray luminosities," lead study author Christian Motch, an astronomer at the University of Strasbourg in France, said to Space.com.
The discovery up for debate is a black hole labeled P13 in the outskirts of the spiral galaxy NGC 7793, which is 12 million light-years away. This black hole is the brightest X-ray source in its galaxy, and was discovered 30 years ago by NASA's Einstein telescope.
The hole has a companion star as well, a blue supergiant 18 to 23 times the mass of the sun, according to the release. A gas from this companion gets sucked into P13, this matter then becomes very hot and bright. The black hole is at least a million times brighter than the sun.
While analyzing the black hole and its companion, the researchers determined that the black hole and its companion star complete a very oval-shaped orbit around each other every 64 days.
"From this, we worked out that the black hole must be less than 15 times the mass of our Sun," said International Centre for Radio Astronomy Research astronomer Dr Roberto Soria, who is based at ICRAR's Curtin University node, according to the release.
Once the black hole reaches the star, the X-rays from it heat up and brighten the side of the star facing the black hole. Astronomers were able to estimate the black hole's mass by modeling this effect, according to the release.
The light that the black hole gives off suggests it gorges on gas at an extraordinary rate, equivalent to the mass of the moon every three weeks, or the mass of Earth every four years. This is much greater than a theoretical maximum known as the Eddington limit.
Their discovery is detailed in the Oct. 9 edition of the journal Nature.
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