 On August 17, 2017, a gravitational wave, traveling at the speed of light, swept across the two LIGO interferometers and the new Virgo interferometer in Italy. The wave was named GW-170817. You may remember from our segment on gravitational waves that the interferometer wave form amplitude, frequency, and change in frequency, called its chirp. Give us a measure of the merging objects mass and distance. This wave form indicated that the masses fit the profile for neutron stars, and that the luminosity distance to the source was around 130 million light years. Location analysis from LIGO limited the direction of the event to two long areas of the sky. As you may have noticed, the Virgo interferometer in Italy did not trigger on the event. This indicates that the angle of impact was one of the four that would not be seen by an interferometer because the instruments arms are impacted in exactly the same way at exactly the same time. This allowed us to narrow the source's location on the sky considerably. One point seven seconds after LIGO triggered, the Fermi Gamma Ray Burst Detector registered Gamma Ray Burst GRB-170817A in an area of the sky that overlaps the area identified by LIGO and Virgo. Simultaneous detection by ESA's integral satellite helped narrow down the Gamma Ray source's possible area of the sky that was completely consistent with the gravitational waves origin. But there are a number of candidate galaxies for the neutron star collision in this area, all at various distances from Earth. But Galaxy NGC 4993, 130 million light years away, looked like a good candidate. This went out to all observatories across the planet and in orbit, that a simultaneous gravitational wave and Gamma Ray Burst had been detected in this area of the sky. Within hours, ground-based telescopes observed optical and near-infrared images of a bright light and named it SSS-17A. Redshift data indicated that it was indeed coming from NGC 4993. Four days later, it had faded significantly. Over the next six days, Hubble captured images of the galaxy invisible and infrared light. Here's an image of the new, bright object that faded noticeably over that time period. This all represents powerful evidence that GW-170817, GRB-170817A and SSS-17A are indeed caused by the same event, the merger of two neutron stars. The combining of gravitational wave detection and electromagnetic detection gives us a whole new avenue of astronomical study.