Universe's Tiniest Black Hole Discovered

[enevitable]

Astronomers have identified the smallest known black hole. The puny object weighs only 3.8 times the Sun's mass and spans just 24 kilometres across.
The black hole is believed to have formed from the collapse of a massive star when it ran out of fuel.
Astronomers are not sure what the smallest possible mass is for black holes formed this way, but they estimate that it is somewhere between 1.7 and 2.7 times the Sun's mass. Less massive objects are expected to collapse into dense neutron stars instead of black holes.
"This black hole is really pushing the limits," says Nikolai Shaposhnikov of NASA's Goddard Space Flight Center in Greenbelt, Maryland, US, who carried out the study with Lev Titarchuk, also of Goddard. "For many years, astronomers have wanted to know the smallest possible size of a black hole, and this little guy is a big step toward answering that question."
The black hole they studied is part of a binary system called XTE J1650-500, where the black hole and an ordinary star orbit around each other. Gas stolen from the ordinary star heats up and emits X-rays as it spirals into the black hole.
Brightening X-rays

As in other similar systems, the intensity of the X-rays rises and falls in a semi-regular way, producing what are known as quasi-periodic oscillations (QPOs). The reason for this is still debated, but some scientists say it is due to gas repeatedly piling up near the black hole and then getting swallowed.
Regardless of how they are produced, the frequency of the QPOs appears to be closely related to the black hole mass. Shaposhnikov and Titarchuk have previously used this relationship to calculate the mass of three other black holes that had already been weighed using well-established techniques and found good agreement between the different approaches.
Now, the two have used the Rossi X-ray Timing Explorer satellite (RXTE) to study QPOs from XTE J1650-500. They calculate the black hole weighs 3.8 times the Sun's mass, with an uncertainty of 0.5 times the Sun's mass. The next smallest black hole with a well-measured mass is called GRO 1655-40. It weighs about 6.3 times the Sun's mass.
Exotic black holes

Even smaller black holes may have been produced in the violence of the universe's earliest moments. Some of these primordial black holes could be microscopic, but so far none of the exotic black holes have been detected.
There is also a chance that microscopic black holes could be created in the Large Hadron Collider particle accelerator due to being operating in 2008. But these black holes should evaporate with a flash of radiation in a fraction of a second.
At the other extreme are black holes with billions of times the mass of the Sun that reside at the centres of some galaxies. The heaviest known weighs as much as 18 billion Suns. By contrast, the black hole at the centre of our Milky Way galaxy weighs about 4 million Suns and is about 20 million kilometres across.
A black hole's size is defined by a boundary called its event horizon. Anything that passes closer to the black hole's centre than the event horizon – including light – is doomed to be swallowed by the black hole.
The new results were presented on Monday at a meeting of the American Astronomical Society's High-Energy Astrophysics Division in Los Angeles, California, US.

Some pretty cool shit, black holes are definately some of the most interesting stuff in the universe, and to think that the smallest possible are 1.7-2.5x the size of our sun



http://space.newscientist.com/articl...iscovered.html

[Smokinscientist]

Well, according to Schwarschild's solutions, a black hole can form anywhere, at anytime. But from an astronomical point of view, this is interesting. This measured mass would not be sufficient for overcome neutron gas pressure, meaning this "black hole" has lost more thant 2/3 its mass.