ASU Nexus for Exoplanet System Science

LIGO and Virgo’s first detection of colliding neutron stars

Image credit: Karan Jani/Georgia Tech

For the first time, light and gravitational-waves were observed resulting from two colliding neutron stars. This is also the first cosmic event that has been observed in both gravitational-waves and light. This observation is a joint effort of LIGO, Virgo and about 70 other ground and space based observatories.

Each observatory consists of an L shaped tunnel in which a beam of laser is sent down each tunnel and reflected back to its origin using suspended mirrors. In the absence of gravitational-waves the light returns back to the start of the tunnel at precisely the same time but in the presence of gravitational-waves the time required for the travel of light in both the tunnels is altered. Neutron stars’ form when massive stars explode in supernovae. They are the smallest and densest stars known to exist. Gravitational-waves were created when two neutron stars spiraled in towards each other and were detected by the observatories for about 100 seconds. The gravitational-signal known as GW170817, resulting from the two neutron stars was detected on Aug. 17, 2017 at 8:41 a.m., Eastern Daylight Time by the two LIGO detectors. Third detector from Virgo helped localize this cosmic event. Following the gravitational-waves a flash of light in the form of gamma rays was observed on Earth after a 2 second delay. This light was caused by the collision of the two neutron stars. Other forms of light such as UV, X-ray, Optical, Infrared and Radio waves were detected as well in the following days. A paper known as GW170817 with results regarding this event has been published in the journal Physical Review Letters.  Signatures of recently synthesized material were observed by the U.S. Gemini Observatory, the European Very Large Telescope and the Hubble Space Telescope which gave scientist’s insight on where half of the heavier than iron elements like gold and platinum are produced. Each electromagnetic observatory will be releasing detailed observation data of this astrophysical event.

Please click here, to access the paper GW170817. Click here for the LIGO press release.

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