Black hole collision reveals clues to early cosmos

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The observatory made its historic first detection of gravitational waves to global fanfare in September 2015, confirming Albert Einstein's prediction of the phenomenon made 100 years before.

"Black holes are beautifully simple, you just need two numbers to describe them completely: a mass, how much they bend space-time, and a spin, how much space-time swirls about them", said Dr Christopher Berry, of the University of Birmingham, one of the researchers in the project.

The new data doesn't actually provide evidence as to whether these specific black holes were moving in a particular direction, but the data does provide the first suggestion that black hole mergers can be non-aligned.

This fills in a gap between the masses of the two merged black holes detected previously by LIGO, which had solar masses of 62 (first detection) and 21 (second detection).

Ripples from that union, which took place about 3 billion light-years from Earth, zoomed across the cosmos at the speed of light, eventually reaching the Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, which detected them on January 4.

"It is remarkable that humans can put together a story, and test it, for such odd and extreme events that took place a billion years ago and a billion light-years distant from us", he said.

Shoemaker is an MIT scientist and newly-elected spokesman for the global group of scientists who perform LIGO research together with the European-based Virgo Collaboration.

The new detection occurred during the ongoing second observing run of the Advanced LIGO detectors in the US, which began on November 30, 2016.

"The entire Ligo and Virgo scientific collaborations worked to put all these pieces together". Its observations are carried out by twin detectors-one in Hanford, Washington, and the other in Livingston, Louisiana-operated by Caltech and MIT with funding from the National Science Foundation (NSF).

Collaborating scientists of the Laser Interferometer Gravitational Wave Observatory - better known as LIGO - reported that they found gravitational waves generated by the merger in a paper placed online June 1 in the journal Physical Review Letters. The pipeline takes the noisy data collected by the LIGO detector and processes it to estimate the precise shape of the gravitational wave signal, independent of any preconceived ideas of what those signals should look like.

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The third and latest detection points to merging black holes that are twice as far away from Earth as the two earlier pairs - about three billion light-years away. The team also used the detection to study how the individual black holes were spinning.

"Now we have three pairs of black holes, each pair ending their death spiral dance over millions or billions of years in some of the most powerful explosions in the universe. The measured properties of the black holes, particularly their individual spin orientations, provide clues to their correct evolutionary paths".

During this hole-on-hole merger, the equivalent of two solar masses were converted into gravitational waves. Prior to a black hole merger like the ones detected by LIGO, two black holes orbit around one another. Gravity Spy engages thousands of "citizen scientists" in classifying these glitches, increasing the chances of success in the gravitational-wave search. They form when each star in a pair of stars explodes, and because the original stars were spinning in alignment, the black holes likely remain aligned.

In the other model, the black holes come together later in life within crowded stellar clusters. Over time, heavy black holes sink to the center of star clusters and, if conditions are right, can pair off into binary systems. The large masses of LIGO's black holes suggest that they formed in such environments. With this, LIGO is starting to create a new branch of science: gravitational wave astronomy.

This finding could favor the formation of some black holes over others. Many LIGO researchers thought they'd start to see some of those smaller singularities.

The find, described Thursday in the journal Physical Review Letters, was made on January 4, about a month after the experiment was switched on for its second run of observation. According to Einstein's theory of gravity, the general theory of relativity, massive objects bend the fabric of space and create ripples when they accelerate - for example, when two objects orbit one another. More than 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration.

"Imagine two tornadoes that are going about each other", said Laura Cadonati, a Georgia Tech physicist and LIGO deputy spokesperson, during a press conference Wednesday. Nevertheless, he says, Einstein's theory of general relativity predicts that space can expand, contract, or vibrate, thereby distorting the medium in which we all live.

"We suspended the run in May so we can make improvements on the detectors, improving their sensitivity", said Thomas Corbitt, an assistant professor of Physics and Astronomy at LSU.

The current data gathering run will go until August, and there's the expectation that the European VIRGO detector will join it in taking data before the summer is over.

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