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Scientists detect first gravitational waves produced by colliding neutron stars

16 October 2017
Artist’s illustration of two merging neutron stars. The narrow beams represent the gamma-ray burst while the rippling spacetime grid indicates the isotropic gravitational waves that characterize the merger.

A large, international team of scientists has directly detected gravitational waves – ripples in space and time – from the spectacular collision of two neutron stars. It marks the first time that a cosmic event has been viewed in both gravitational waves and light.

The detection was made using the US-based Laser Interferometer Gravitational-Wave Observatory (LIGO); the Europe-based Virgo detector; and approximately 70 ground and space-based observatories.

Neutron stars are the smallest, densest stars known to exist and are formed when massive stars explode in supernovae. As these particular neutron stars spiralled 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 collision, other forms of light, or electromagnetic radiation — including X-ray, ultraviolet, optical, infrared, and radio waves — were detected.

Professor Mark Sullivan and Postdoctoral Fellow Dr Cosimo Inserra, of Physics and Astronomy, are part of the ePESSTO collaboration that led a Nature paper on the electromagnetic observation of this new neutron star event. It revealed a transient that has physical parameters that broadly match the theoretical predictions from neutron-star mergers (a ‘kilonova’), as well as the first direct evidence that such events are a major source for the synthesis of elements heavier then iron. Dr. Inserra comments, “The optical observations we made of this gravitational wave source revealed an astronomical event unlike any other previously observed. Our data show that events like this can be a major source for creating the very heaviest elements in the universe.”

Professor Ian Jones, Dr Wynn Ho and PhD student Emma Osborne from Mathematical Sciences at the University of Southampton, are part of the 1,200 strong LIGO team, made up of scientists from 16 different countries around the world. The LIGO-Virgo results are published today (16 October 2017) in the journal Physical Review Letters, with the ePESSTO observations of the electromagnetic counterpart published in Nature. Additional papers from the LIGO and Virgo collaborations and the astronomical community have been either submitted or accepted for publication in various journals.

In the weeks and months ahead, telescopes around the world will continue to observe the afterglow of the neutron star merger and gather further evidence about its various stages, its interaction with its surroundings, and the processes that produce the heaviest elements in the universe.

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