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LIGO team announced second detection of gravitational waves

Jun 17, 2016 08:10 IST

Laser Interferometer Gravitational-Wave Observatory (LIGO) team on 15 June 2016 announced their second detection of gravitational waves, the flexing of space and time caused by the black hole collision.

The detection was made on 26 December 2016 by the LIGO’s twin detectors in Louisiana and Washington when the waves hit the observatory lasted for about a full second and is five times longer than the first one.

While, the first gravitational wave observation was announced in February 2016 by LIGO and the discovery was published in Physical Review Letters. The waves first hit the observatory in Livingston, Louisiana, and then 1.1 milliseconds later passed through the one in Hanford, Washington on 14 September 2015.


• Two black holes spiraled toward each other in deep space with their tremendous mass warping space time and propagating gravitational waves across the fabric of the universe at light-speed.

• The two black holes crashed into one another and merged into one even bigger black hole which is 62 times the mass of the Sun, emitting a crescendo of waves.

• The two LIGO detectors measured gravitational waves from the inspiral, as the decaying mutual orbits of two bodies and merger of two black holes. One was eight and the other 14 times the Sun’s mass, both merged to form a black hole with 21 times the solar mass.

Hubble Image

• The signal from the first collision LIGO detected, for instance, only lasted for about 0.2 seconds.

• Smaller black holes can get much closer before they collide, so they can spend much longer orbiting faster than LIGO’s minimum threshold.

About LIGO detectors

• These detectors are shaped like a giant letter L, built out of two 2.5 mile-long vacuums.

• Light travels down each leg before bouncing off an 88 pound mirror dangling from a system of pulleys held by pulleys connected to equipment that actively measures and counteracts the seismic motion of the Earth.

• Each pulley naturally dissipates any motion that gets through, and the system magnifies the effect for four times.

• The light recombines in a detector at the crux of the L.

• If the mirrors are exactly where they should be, the crests of one ray line up with the troughs of the other, and no light hits the detector.

• If the mirrors move at all, the rays line up imperfectly and some light ekes through, by alerting the system to look for sources of error.

• Everything from magnets in the sensors to acoustic noise around the vacuum tubes to passing trucks can create noise in the measurements.

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