A New Type of Black Hole Has Been Discovered: Here's What We Know
Scientists have discovered a possible new type of black hole – and though it be but little, it is fierce. According to reports from CNN, astronomers were taking a "census" of black holes when they realized they had stumbled upon a novel way of detecting black holes… One that forced them to challenge their assumptions about how black holes form in the first place. The study was published yesterday in the journal Science.
Todd Thompson, an astronomy professor at Ohio State University and the lead author of the study, summarized, "What we've done here is come up with a new way to search for black holes, but we've also potentially identified one of the first of a new class of low-mass black holes that astronomers hadn't previously known about."
Black holes are hypergravitational vortices of supremely dense matter that exert a force so strong that not even light can escape. The majority of black holes that we know of form in the aftermath of a supernova – a giant star about three times the mass of our Sun exploding and then collapsing in on itself. There could be as many as 10 million to 1 billion black holes just in our Milky Way galaxy.
Traditional methods for locating black holes depend on measuring the X-ray radiation that is emitted when large objects like stars pass near a black hole and some of their matter is cannibalized and sucked into the vortex. Scientists know that black holes also form in binary star systems, where two stars are locked together in orbit.
Thompson and his team decided to investigate these binary star systems using data to observe the light emitted from them to analyze any changes in its wavelength. If the light from one of the stars shifted (specifically from blue to red in accordance with Einstein's now-proven theory of gravitational redshift) it could be evidence that its companion star had turned into a black hole.
They found something surprising: in one binary star system, a large reddish star was orbiting something that was not-quite-a-star, and not-quite-a-black-hole. It's 3.3 times the mass of our Sun (which just barely fits the bill for black hole formation), but the smallest black hole on record is 3.8 times as massive as our home star. That said, astronomers are fairly confident in their discovery and say its applications will ripple across their field:
"…If we could reveal a new population of black holes, it would tell us more about which stars explode, which don't, which form black holes, which form neutron stars. It opens up a new area of study," Thompson declared.
Watch this video from NASA as the Rossi X-ray Timing Explorer (RXTE) instrument "listens" to what was previously believed to be the smallest black hole possible: