By Xinhua
Washington : Two astronomers at NASA’s Goddard Space Flight Center have identified the smallest known black hole in the universe, according to the Astrophysical Journal on Wednesday.
The two astronomers presented their results this week at an American Astronomical Society meeting.
This black hole weighs the same as 3.8 of our Sun. But it’s a pipsqueak when compared to all other known black holes. Previously, the smallest known black hole would weigh about 6.3 times as much as the Sun, and some black holes tip the scales at millions or even billions of times that of our Sun.
The new record holder belongs to a binary system named XTE J1650, in which the black hole is orbited by a companion star.
Black holes formed in the center of dying stars. The star’s core was a giant nuclear reactor, generating energy by turning light elements such as hydrogen into heavier elements such as oxygen. But eventually, the reactor ran out of fuel and shut down. The core collapsed due to its own gravity and formed a black hole.
Astronomers think that this process can form black holes down to about 3 times the weight of our Sun. So the XTE J1650 black hole is not only the lightest known black hole, it’s close to the smallest possible size for a black hole.
The two astronomers made their discovery by using NASA’s Rossi X-ray Timing Explorer, a small satellite that launched in late 1995.
Rossi is able to make extremely precise measurements of gas whirling around black holes. By timing the motion of the gas, astronomers were able to measure the strength of the black hole’s gravitational field, which tells them how much it weighs.