When did LIGO discover gravitational waves?

Gravitational waves

A hundred years ago Albert Einstein predicted the existence of gravitational waves. The first direct evidence was provided in September 2015 - a milestone. Since then, the distortions of space-time have allowed completely new insights into the universe.

Albert Einstein postulated gravitational waves as early as 1916. These distortions of spacetime arise as a direct consequence of his general theory of relativity. Since then, physicists have tried to track down these waves - on the one hand to confirm Einstein's theory one more time, on the other hand because the waves promise new knowledge about the universe and its formation.

On September 14, 2015, the first direct detection of gravitational waves with the Advanced LIGO detectors was achieved in the USA. The measured signal came from two black holes that circled each other, came closer and closer and finally merged with each other. On August 14, 2017, three detectors recorded a signal simultaneously for the first time - in addition to the Advanced LIGO detectors, the Advanced Virgo gravitational wave detector in Italy was also involved this time. The triple measurement significantly improves the accuracy with which the sky position and distance of the compact objects can be determined.

On August 17, 2017, astronomers received both electromagnetic radiation and gravitational waves from an event for the first time: In the 130 million light-years distant galaxy NGC 4993, two neutron stars collided and merged. This marks the beginning of a new age in gravitational wave astronomy, according to the scientists. In October 2020, the LIGO and Virgo collaborations published an updated gravitational wave catalog that now includes a total of fifty signals. The vast majority of the signals observed so far - a total of 46 events - are due to merging black holes.

The amalgamation of compact objects discovered so far by LIGO and Virgo