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LIGO Detects Gravitational Waves for Third Time

The Laser Interferometer Gravitational-wave Observatory (LIGO) has made a third detection of gravitational waves, ripples in space and time, demonstrating that a new window in astronomy has been firmly opened. This is announced on June 1, 2017.

The third detection, called GW170104 and made on January 4, 2017, occurred during LIGO's current observing run, which began November 30, 2016, and will continue through the summer. The LIGO Scientific Collaboration and Virgo Collaboratio described it in a new paper accepted for publication in the journal Physical Review Letters.

As was the case with the first two detections, the waves were generated when two black holes collided to form a larger black hole. The newfound black hole, formed by the merger, has a mass about 49 times that of our sun. This fills in a gap between the masses of the two merged black holes detected previously by LIGO, with solar masses of 62 (first detection) and 21 (second detection).

In all three cases, each of the twin detectors of LIGO detected gravitational waves from the tremendously energetic mergers of black hole pairs. These are collisions that produce more power than is radiated as light by all the stars and galaxies in the universe at any given time. The recent detection appears to be the farthest yet, with the black holes located about 3 billion light-years away. (The black holes in the first and second detections are located 1.3 and 1.4 billion light-years away, respectively.)

The twin LIGO detectors, located in Livingston, Louisiana, and Hanford, Washington, USA, is funded by the National Science Foundation (NSF), and operated by MIT and Caltech, which conceived and built the project. Financial support for the Advanced LIGO project was led by NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project. More than 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. LIGO partners with the Virgo Collaboration, a consortium including 280 additional scientists throughout Europe supported by the Centre National de la Recherche Scientifique (CNRS), the Istituto Nazionale di Fisica Nucleare (INFN), and Nikhef, as well as Virgo’s host institution, the European Gravitational Observatory. Additional partners are listed at: http://ligo.org/partners.php.

The LIGO Scientific Collaboration research group at Tsinghua University includes Junwei Cao and Xilong Fan from Research Institute of Information Technology, and Zhihui Du and Xiangyu Guo from Department of Computer Science and Technology. The group has been a formal member of LIGO Scientific Collaboration since 2009. The group is focused on algorithm design, performance optimization, and software development of gravitational wave data analysis, contributing to the three gravitational waves detections so far.


An Illustration of Binary Black Holes.


Waveforms of the Detected Gravitational Waves.