Gravitational waves detected from more colliding black holes

Theground-breaking detection of gravitational waves, ripples inspace and time postulated by Albert Einstein 100 years ago, thatwas announced in February was no fluke. Scientists said onWednesday that they have spotted them for a second time.

The researchers said they detected gravitational waves thatwashed over Earth after two distant black holes spiralled towardeach other and merged into a single, larger abyss 1.4 billionyears ago. That long-ago violent collision set off
reverberations throughspacetime, a fusion of the concepts oftime and three-dimensional space.

These gravitational waves were observed by twinobservatories in the United States late on Dec. 25, 2015 (early
on Dec. 26 GMT). The detectors are located in Livingston,Louisiana, andHanford, Washington.

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The first detection of gravitational waves was made inSeptember and announced on Feb. 11. It created ascientific sensation and was a benchmark in physics andastronomy, transforming a quirky implication of Einstein's 1916theory of gravity into the realm of observational astronomy.

The waves detected in September and December both weretriggered by the merger of black holes, which are regions sodense with matter that not even photons of light can escape thegravitational sinkholes they produce in space.

Upgraded sensitivity

The merging black holes that set space ringing in Decemberwere much smaller than the first pair, demonstrating the
sensitivity of the recently upgraded Laser InterferometerGravitational-wave Observatory, or LIGO, facilities.

"We are starting to get a glimpse of the kind of newastrophysical information that can only come fromgravitational-wave detectors," said Massachusetts Institute ofTechnology researcher David Shoemaker.

The black holes that triggered the newly detectedgravitational waves were eight and 14 times more massive than
the sun, respectively, before merging into a single, spinningblack hole about 21 times more massive than the sun. The
equivalent of one sun's worth of mass was transformed intogravitational energy.

The Louisiana site detected the waves first and theWashington state detector picked up the signal 1.1 milliseconds
later. Scientists can use the timing difference to calculate arough idea of where the black holes merger occurred.

Scientists say the second detection confirms that pairs ofblack holes are relatively common.

"Now that we are able to detect gravitational waves, theyare going to be a phenomenal source of new information about ourgalaxy and an entirely new channel for discoveries about theuniverse," Pennsylvania State University astrophysicist ChadHanna said.

The research, presented at the American Astronomical Societymeeting in San Diego, will be published in the journal PhysicalReview Letters.

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