February 2016

Direct detection of gravitational waves

Predicted by Einstein 100 years ago, gravitational waves have now been directly detected for the first time. The signal of two merging black holes has been found by the LIGO detectors in Hanford and Livingston, USA.

On September 14, 2015, at 11:50:45 CEST both LIGO detectors registered the same signal, offset by 7 ms. It corresponds to that of two black holes, orbiting each other with increasing velocity, and merging finally. The frequency increases in 0.2 seconds from 35 Hz to 150 Hz, with a maximum signal amplitude of  10^-21.  The two black holes had 29  and 36 times the mass of our Sun, respectively. The black hole created in the merger has 62 solar masses, meaning that 3 solar masses have been converted into energy in form of gravitational waves.

The increased sensitivity of the LIGO detectors is based on many technologies developed and tested at GEO600: powerful lasers from the Laser Zentrum Hannover and the Albert Einstein Institute in Hannover, monolithic mirror suspensions, and power and signal recycling.

At 16:30 CEST on February 11, 2016, the discovery was announced in press conferences, one of which took place in Hannover.