LIGO Announces Detection of Gravitational Waves

Gabriela González, LSU: LIGO Scientific Spokesperson

David Reitze, Cal Tech: LIGO Laboratory Director

The LIGO Collaboration Announces Detection of Gravitational Waves

February 11, 2016; Washington, DC, USA

The Laser Interferometer Gravitational-Wave Observatory is a large-scale physics experiment aiming to directly detect gravitational waves. David Reitze, LIGO Laboratory Executive Director (Cal Tech) said, "We. Have. Detected. Gravitational waves! We did it." The signal they saw was exactly what was predicted by Albert Einstein's General Theory of Relativity for a collapsing binary black hole system. These two black holes have a mass of 30 suns. Furthermore, this is proof that binary black holes exist.

Gabriela González, LIGO Scientific Spokesperson (LSU), presented the results from measurements made on September 14, 2015, which shows the distortion of the LIGO detector at Hanford, Washington (USA), which translated to a distortion of a fraction of the diameter of a proton. It was a twin signal, matching exactly what has been predected, spaced by 7 milliseconds -- again, exactly as predicted. The same signal, at the same time, was observed at the LIGO detector in Livingston, Louisiana (USA). She noted that the energy rleased by these gravitational waves was equivalent to three solar masses.

The paper has been published on Physical Review Letters. Here is the abstract:

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410+160−180  Mpc corresponding to a redshift z=0.09+0.03−0.04. In the source frame, the initial black hole masses are 36+5−4M⊙ and 29+4−4M⊙, and the final black hole mass is 62+4−4M⊙, with 3.0+0.5−0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

From the New York Times:

A team of physicists who can now count themselves as astronomers announced on Thursday that they had heard and recorded the sound of two black holes colliding a billion light-years away, a fleeting chirp that fulfilled the last prophecy of Einstein’s general theory of relativity.

That faint rising tone, physicists say, is the first direct evidence of gravitational waves, the ripples in the fabric of space-time that Einstein predicted a century ago (Listen to it here.). And it is a ringing (pun intended) confirmation of the nature of black holes, the bottomless gravitational pits from which not even light can escape, which were the most foreboding (and unwelcome) part of his theory.

More generally, it means that scientists have finally tapped into the deepest register of physical reality, where the weirdest and wildest implications of Einstein’s universe become manifest.

This work has been supported by the National Science Foundation over the last 40 years.