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08 February 2016

UPDATE! Gravitational waves ... detected!

Prior to sealing up the chamber and pumping the
vacuum system down, a LIGO optics technician
inspects one of LIGO’s core optics (mirrors) by
illuminating its surface with light at a glancing angle.
It is critical to LIGO's operation that there is no
contamination on any of its optical surfaces.
Credit: Matt Heintze/Caltech/MIT/LIGO Lab
Update, 11 February: A hundred years after Einstein predicted them, gravitational waves from a cataclysmic event a billion years ago have been observed.

For the first time, scientists have observed gravitational waves, ripples in the fabric of spacetime arriving at Earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein's 1915 general theory of relativity and opens an unprecedented new window to the cosmos.

The discovery was announced on 11 February at a press conference in Washington, DC, hosted by the National Science Foundation, the primary funder of the Laser Interferometer Gravitational Wave Observatory (LIGO).

The gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.

The event took place on 14 September 2015 at 5:51 a.m. EDT (09:51 UTC) by both of the twin (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington. The LIGO observatories are funded by the National Science Foundation (NSF), and were conceived, built and are operated by the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT).


Earlier this week (on 8 February), we wrote:

Gravitational wave rumors pulsate through media


The control room of the LIGO Hanford detector site
near Hanford, Washington. Credit: Caltech/MIT/LIGO Lab
The cosmic rumor mill has been busy lately with tweets and lots of buzz about a potential announcement of observation of gravitational waves by the Laser Interferometer Gravitational Wave Observatory (LIGO). Predicted by Einstein 100 years ago, gravitational waves are ripples in space-time caused by collisions of massive objects like black holes and neutron star.

The LIGO interferometers in Louisiana and Washington State were just retooled, based on what researchers learned from their first few years of observations from 2002 to 2010. They are already several times more sensitive, and as the instruments are tuned to design sensitivity, they will be even better. According to some reports, their first observing run may have already found something. We’ll know on 11 February and we will update this post after that. Until then, see these reports:



The SPIE Newsroom visited LIGO Hanford Observatory last fall, just after the first observing run began for Advanced LIGO. In the following video, observatory Head Frederick Raab and LIGO Hanford Lead Scientist Mike Landry introduce us to the instrumentation and setup of LIGO Hanford, from the laser whose beam travels through the 4-km tubes of LIGO, to the stabilization needed for the interferometer’s mirrors: