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Scientists detect Einstein gravitational waves for a third time

02 June 2017

The three detections made so far come from two labs that form part of the Laser Interferometer Gravitational-Wave Observatory (LIGO).

Once is chance, twice is coincidence, thrice is a pattern.

Three billion years ago, in a third of a second, two black holes crashed into each other and merged into a single entity, converting two solar masses into energy that shook the fabric of spacetime, sending gravitational ripples across the universe that were detected on Earth last January, researchers announced Thursday.

An OzGrav animation depicting the binary black hole merger event GW170104, detected by LIGO.

Researchers have now confirmed that a third black hole merger was detected on 4 January 2017, earning it the memorable name GW170104.

The recent detection is the farthest yet, with the black holes located about 3 billion light-years away.

"If neutron stars have small deformities in their crust, or minute "mountains" on them, then as they rotate the changing mass configuration with each rotation due to these asymmetries will produce a continuous stream of gravitational waves", says Scott. If the black holes formed together, each one should spin in the same direction as the overall orbital motion (the spiral).

The hint of information about the black holes' spins in the latest event has prompted much dicussion among the collaboration about how much insight could be gleaned from it. But if the black holes instead find one another in the chaos of a star cluster, they could spin any which way.

"We now have further confirmation of the existence of stellar-mass black holes that are larger than 20 solar masses - these are objects we didn't know existed before LIGO detected them", said MIT's David Shoemaker, spokesperson for the LIGO Scientific Collaboration (LSC), a body of more than 1,000 worldwide scientists who perform LIGO research together with the European-based Virgo Collaboration.

While it might be hard to picture, black holes can actually spin. Two times the mass of Earth's sun was converted directly into energy in a fraction of a second.

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This 3-D projection of the Milky Way galaxy onto a transparent globe shows the probable locations of three black-hole merger events, plus a fourth possible detection at lower significance (LVT151012, green).

One drawback of having just the two detectors at Hanford, Washington and Livingston, Louisiana tuned to detect gravitational waves is that they can not accurately figure out where in the sky the signal is coming from.

"We continue to learn more about this population of heavy stellar-mass black holes, with masses over 20 solar masses, that LIGO has discovered", said LIGO collaborator Ben Farr, a McCormick Fellow at UChicago's Enrico Fermi Institute.

The LIGO Scientific Collaboration is an global collaboration whose observations are carried out by twin detectors-one in Hanford, Wash., and the other in Livingston, La. -operated by California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation.

"As was the case with the first two detections, the waves detected in our new paper were generated when two black holes merged to form a larger black hole". LIGO has done a lot of work in a short amount of time; it's exciting to think about what might be ahead as the observatory turns its attention to other types of astronomical events, such as the collision of neutron stars. GEO600 is the only gravitational-wave detector worldwide using squeezed light to mitigate fundamental quantum noise effects and improve its sensitivity at high frequencies.

"The black holes are not necessarily lined up", said Professor Scott, of the Australian National University, one of several Australian universities involved in the research.

LIGO's first discovery of gravitational waves happened in September 2015.

No wonder we can detect the shock waves of such a distant event.

Alternatively, they may have formed separately, then come together in the densely packed star clusters in which their parent stars existed. Georgia Tech astrophysicist Laura Cadonati on Wednesday likened the spinning black holes to a pair of tornadoes that dance around each other. They collaborate with computer scientists at Northwestern's Image and Video Processing Laboratory, the Zooniverse team at Chicago's Adler Planetarium, human-computer interaction experts at Syracuse University and LIGO scientists at California State University, Fullerton.

LIGO is funded by the National Science Foundation (NSF), and operated by MIT and Caltech, which conceived and built the project. The NSF led in financial support for the Advanced LIGO project with Germany (MPG), the U.K. (STFC) and Australia (ARC) making significant commitments and contributions to the project.

Scientists detect Einstein gravitational waves for a third time