LIGO Document G1601664-v1

LIGO and the beginning of gravitational wave astronomy

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Gravitational waves are ripples in the fabric of spacetime produced by some of the most energetic astrophysical events in the Universe. These spacetime waves are very weakly interacting. This makes them difficult to detect, but allows us to observe the interior dynamics of violent systems that are obscured to telescopes, which rely on radiated light. The Advanced LIGO detectors are engineered to sense gravitational waves, which produce tiny fluctuations in the relative distance between points in space as they pass. The detectors' sensitivity is equivalent to measuring a change in distance between Earth and Alpha Centauri, the closest star to our sun, as small as the thickness of a human hair.

On September 14, 2015, LIGO made history with the detection of gravitational waves from binary black hole merger GW150914. 1.3 billion years prior and far, far away, two black holes about 36 and 29 times the mass of the sun collided, forming a bigger black hole roughly 62 times the mass of the sun. This event radiated an enormous amount of energy in gravitational waves in less than 20 milliseconds; more energy than 3 suns would radiate over many billions of years. GW150914 was the first direct detection of gravitational waves, a prediction of Einstein's theory of general relativity, and the first observation of a binary black hole merger. During the same observing run, LIGO discovered another gravitational wave signal from a different binary black hole merger on December 26, 2015 (GW151226). These observed events reveal a population of binary black hole systems in the Universe with mass and spin properties never before measured.

This talk will cover astrophysical sources of gravitational waves, the gravitational wave signals detected during Advanced LIGO’s first observing run, noise sources and technical challenges for the Advanced LIGO detectors, and the prospects for future observing runs.

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