Edinburgh PhD student helps chart neutron star collision

Edinburgh scientists have taken part in the first detection and analysis of a powerful astronomical event – the merger of two very dense neutron stars.

The results give unprecedented insight into the processes involved when neutron stars collide in deep space.  The event, some 130 million light years away, is the latest discovery made using sophisticated gravitational wave detectors.

It is the first binary neutron star collision to be observed by the international Laser Interferometer Gravitational Wave Observatory (LIGO) collaboration, and the first gravitational wave event to be observed by conventional telescopes.

Multiple sources

Observing the same event in different ways provides much more information about the processes involved when neutron stars collide in deep space.  It has also allowed a measurement of the rate at which the universe is expanding – known to scientists as Hubble’s constant. 

David Homan, a PhD student from the School of Physics and Astronomy was working at the NTT telescope in Chile when the team there was alerted to the event.  Jonathan Gair, a researcher from the School of Mathematics also took part in the gravitational wave data analysis and scientific interpretation of the event.  They were able to capture some of the first visible evidence of it, and to track its development over several days.  Energy in the form of gravitational waves, gamma rays, X-rays, light and radio waves was detected in the aftermath of the collision, helping astronomers around the world confirm and characterise the event.

Scientific insights

The collision offers valuable insight into elusive explosions known as gamma ray bursts.  A type of gamma ray burst can occur in the aftermath of a binary neutron star collision.  These emit energy equivalent to that produced by an entire galaxy in a year, in a matter of seconds.

Scientists also found evidence of a kilonova event – an outburst of visible light that astronomers had predicted may occur following a neutron star merger, as a by-product of the production of heavy chemical elements.

The international LIGO team gathers and analyses data from a pair of highly sensitive detectors in the US.  Measurements from an additional gravitational wave detector in Italy, named Virgo, helped scientists pinpoint the location of recorded events.  The detectors were conceived to demonstrate the existence of gravitational waves, which are ripples in spacetime created by extreme astronomical events, and for use as a revolutionary new kind of telescope.

Nobel-winning research

Gravitational waves were detected for the first time in 2015, a discovery that led to the award of the 2017 Nobel Prize for Physics.  Latest findings from the international collaboration have been published in a series of scientific papers including Physical Review Letters and Nature.

David Homan reported:  “This is truly an exceptional discovery: a never before seen event with the potential for many new insights and discoveries. Given the size of the collaborative effort involved, from LIGO and Virgo to different observatories around the world, I am just excited to have played a small part.”

A consortium of European astronomers are involved in a project aimed at catching the spectra of transient events.  Included in this is Professor Andy Lawrence from the School of Physics and Astronomy.   

Professor Andy Lawrence announced:  "This is the culmination of the hard work of hundreds of people over decades.  But it is also the start of something new - multi-messenger astrophysics!  We can learn about the Universe from light, gravitational waves and particles all at the same time.”

The UK contribution to LIGO is supported by the Science and Technology Facilities Council.