Neutron star smashup seen for first time, ‘transforms’ understanding of Universe


Scientists have for the first time witnessed the crash of two ultra-dense neutron stars, cataclysmic events now known to have generated at least half the gold in the Universe, excited research teams revealed Monday.

Shockwaves and light flashes emitted by the cosmic fireball travelled some 130 million light-years to be captured by Earthly detectors on August 17, they revealed at simultaneous press conferences around the globe as a dozen science papers were published in top academic journals.

“We witnessed history unfolding in front of our eyes: two neutron stars drawing closer, closer… turning faster and faster around each other, then colliding and scattering debris all over the place,” co-discoverer Benoit Mours of France’s CNRS research institute told AFP.

The groundbreaking observation solved a number of physics riddles and sent ripples of anticipation through the scientific community.

Most jaw-dropping for many, the data finally revealed where much of the gold, platinum, mercury and other heavy elements in the universe came from.

Telescopes saw evidence of newly-forged material in the fallout, the teams said — a source long suspected, now confirmed.

“It makes it quite clear that a significant fraction, maybe half, maybe more, of the heavy elements in the Universe are actually produced by this kind of collision,” said physicist Patrick Sutton, a member of the Laser Interferometer Gravitational-Wave Observatory (LIGO) which contributed to the find.

Neutron stars are the condensed, burnt-out cores that remain when massive stars run out of fuel, blow up, and die.

Some 20 kilometres in diameter, with slightly more mass than our sun, they are highly radioactive and ultra-dense — a handful of material from one weighs as much as Mount Everest.

‘Too beautiful’

It had been theorised that mergers of two such exotic bodies would create ripples in the fabric of space-time known as gravitational waves, as well as bright flashes of high-energy radiation called gamma ray bursts.

On August 17, detectors witnessed both phenomena, 1.7 seconds apart, coming from the same spot in the constellation of Hydra.

“It was clear to us within minutes that we had a binary neutron star detection,” said David Shoemaker, another member of LIGO, which has detectors in Livingston, Louisiana and Hanford, Washington.

“The signals were much too beautiful to be anything but that,” he told AFP.

The observation was the fruit of years of labour by thousands of scientists at more than 70 ground- and space-based observatories scattered around the globe.

Along with LIGO, they included teams from Europe’s Virgo gravitational wave detector in Italy, and a number of ground- and space-based telescopes including NASA’s Hubble.

“This event marks a turning point in observational astronomy and will lead to a treasure trove of scientific results,” said Bangalore Sathyaprakash from Cardiff University’s School of Physics and Astronomy.

The detection is another feather in the cap for German physicist Albert Einstein, who first predicted gravitational waves more than 100 years ago.

Three LIGO pioneers, Barry Barish, Kip Thorne and Rainer Weiss, were awarded the Nobel Physics Prize this month for the observation of gravitational waves, without which the latest discovery would not have been possible.

The ripples have been observed four times before now — the first time by LIGO in September 2015.

The fifth and latest gravitational wave observation is the first from a neutron star fusion. The other four were from black hole mergers which are even more violent but unlike neutron stars, emit no light.

‘Earlier’ than expected

The latest wave observation, on the other hand, was accompanied by flashes of gamma rays, which scientists said came from closer in the Universe and were less bright than expected.

“What this event is telling us is that there may be many more of these short gamma ray bursts going off nearby in the Universe than we expected,” Sutton said.

“This might be the tip of the iceberg of short gamma ray bursts produced by collisions and mergers of neutron stars” — an exciting prospect for scientists hoping to uncover further secrets of the Universe.

Among other things, it is hoped that data from neutron star collisions will one day reveal the rate of expansion of the cosmos, which in turn would tell us how old it is and how much matter it contains.

“It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the Universe,” said France Cordova, director of the National Science Foundation which funds LIGO.
— Agence France-Presse