Gravitational waves caused by colliding neutron stars a ‘massive’ discovery

16 Oct 2017

Artist’s impression of the collision of two neutron stars that created the gravitational waves. Image: ESO/L Calçada/M Kornmesser

What we know about gravitational waves and how they teach us about the distant universe has been blown wide open again.

The detection of gravitational waves in 2015 has thrown open a whole new avenue of research for astronomers and astrophysicists, and the latest news from the Laser Interferometer Gravitational-Wave Observatory (LIGO) is being described as massive, to say the least.

In an announcement today (16 October), LIGO and the European Southern Observatory confirmed they had detected both gravitational waves and a light source for the first time ever, created following the collision of two neutron stars approximately 100m years ago.

The cosmic event was detected on 17 August and was evidence of space time rippling resulting from the merging of two of these extremely dense, compact objects.

The cataclysmic aftermaths of this kind of merger – long-predicted events called kilonovae – disperse heavy elements such as gold and platinum throughout the universe.

Distance estimates from both the gravitational wave data and other observations agree that GW170817 (the name for the detection) was at the same distance as NGC 4993, about 130m light years from Earth.

This makes the source both the closest gravitational wave event detected so far and also one of the closest gamma-ray burst sources ever seen.

The initial detection was immediately followed by a burst of gamma-rays detected by two space observatories, NASA’s Fermi satellite and the European Space Agency’s Integral satellite.

With help from thousands of scientists across the globe, LIGO was then able to use other ground-based telescopes to confirm the fading afterglow of a typical gamma-ray burst.

One of those scientists was Elena Pian, an Italian astronomer and lead author of one of the scientific papers documenting the discovery, who said: “There are rare occasions when a scientist has the chance to witness a new era at its beginning. This is one such time!

Irish flavour to discovery

There was some Irish flavour to this discovery, with three of the scientists involved coming from the Dublin Institute for Advanced Studies (DIAS), including Prof Felix Aharonian, Prof Luke Drury and Dr Carlo Romoli.

Drury said: “This is truly an exciting discovery and, along with my DIAS School of Cosmic Physics colleagues, we are delighted to have taken part in it.”

He added that with the recent detection of a fourth gravitational wave and the awarding of the Nobel Prize in Physics to the three scientists instrumental in its discovery, this latest result “marks the beginning of a totally new era” in astronomy.

The closeness of this announcement to the one in September alludes to the suggestion that by next year, the detection of gravitational waves would become as frequent as weekly, as our understanding and ability to detect them rapidly increases.

Colm Gorey was a senior journalist with Silicon Republic