For the first time, on August 17th 2017, scientists have directly detected gravitational waves — ripples in space-time — in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light.
The discovery was made using the Europe-based Virgo detector, the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and some 70 ground- and space-based observatories. The new scientific result was announced on October 16th in a press conference in Washington, with representatives from the Virgo and LIGO Collaborations and from the teams which contributed to the observations.
The reasearch group led by Prof. Viviana Fafone of the Physics Department and INFN unit, is part of the Virgo Collaboration and actively contributes to the project, with major responsibilities in the development of the detector and in the analysis of the data collected.
Neutron stars are the smallest, densest stars known to exist and are formed when massive stars explode in supernovas. As these neutron stars spiraled together, they emitted gravitational waves that were detectable for about 100 seconds; when they collided, a flash of light in the form of gamma rays was emitted and seen on Earth about two seconds after the gravitational waves. In the days and weeks following the smashup, other forms of light, or electromagnetic radiation — including X-ray, ultraviolet, optical, infrared, and radio waves — were detected.
The observations have given astronomers an unprecedented opportunity to probe a collision of two neutron stars and have provided new esperimental evidences such as the signatures of recently synthesized material, including gold and platinum, solving a decades-long mystery of where about half of all elements heavier than iron are produced.
The LIGO-Virgo results are published in the journal Physical Review Letters; additional papers from the LIGO and Virgo collaborations and the astronomical community are published in various top ranked journals.