Astrophysicists discover incredible origin of gold

Tuesday, 17 Oct, 2017

The extraordinary event was first picked up on August 17th of this year when the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the U.S. alongside the VIRGO interferometer in Italy recorded gravitational waves hitting Earth as the neutron stars came together for about 100 seconds. Over the a year ago and a half, gravity wave detection has become fairly routine.

Professor Laura Cadonati, from Georgia Institute of Technology, and the Laser Interferometer Gravitational-Wave Observatory (Ligo), which first observed gravitational waves in 2015, said: "This detection has genuinely opened the doors to a new way of doing astrophysics". Scientists could identify the chirp source as objects that were much less massive than the black holes seen to date. Each of these bands of the electromagnetic spectrum yields different kinds of information about the source, allowing the researchers to study this neutron-star collision in unprecedented detail.

The observation of ripples in space and time by an global team of astronomers, including dozens from Australia, comes less than a month after the discovery of gravitational waves won the 2017 Nobel Prize in Physics.

The gravitational waves had been predicted by Einstein in 1916, as an outgrowth of his groundbreaking general theory of relativity, which depicted gravity as a distortion of space and time triggered by the presence of matter. September's announcement proved him right, although he himself thought we'd never be able to detect them, the results being so slight. After a long dance toward each other, two neutron stars - one somewhere around 1.1 solar masses, the other weighing in the neighborhood of 1.6 suns - finally collided, converting some of their combined mass into gravitational waves. The signal of that cataclysm reached Earth at 5:41 a.m. PDT on August 17. Usually, this is followed by a supernova, where the outer layer of the star blows off in a colossal explosion. According to Daniel Holz, an astrophysicist at the University of Chicago, "back-of-the-envelope calculations indicate that this single collision produced an amount of gold greater than the weight of the Earth".

The two neutron stars smashing into each other creates a kilonova, which is also expected to throw heavy elements into space. "These neutron star mergers are believed to be one of the most important sites where heavy elements are made".

A neutron star is the burnt-out core of a massive star that ran out of fuel, blew up and died.

Artist's concept of the explosive collision of two neutron stars. Neutron stars are the second densest known objects in the universe after black holes, and both form under similar circumstances. Astronomers needed to see the event in visible light. LIGO is comprised of two observatories, one in Hanford, Washington, and the other in Livingston, Louisiana.

The collaborative effort between LIGO, Virgo, and multiple additional observatories demonstrates the power of these instruments to find smaller and smaller gravitational events. Other such observatories are in the works for Japan and India, which will further help pinpoint an event's location.

LIGO's detectors consist of two L-shaped arms, each several kilometers long. When there are no gravitational fluctuations, the laser bounces back normally.

ANU astronomer Dr Christian Wolf says his team used the SkyMapper and 2.3-metre telescopes at the ANU Siding Spring Observatory as part of the search for other signals from the neutron star collision.

The cosmic crash described Monday occurred about 130 million light-years away in the constellation Hydra, said David Reitze, executive director of the LIGO Laboratory at Caltech. In a press release, he explained the importance of the groundbreaking even.

So catastrophically powerful was the collision between two neutron stars - measuring about 12km in diameter each - that it made ripples in the very fabric of the universe, leading to the fifth detection of gravitational waves on Earth.

The event also solidified another of Einstein's predictions.

Less than a month after three United States professors were awarded the Nobel Prize in Physics for the 2105 discovery of gravitational waves, a team of Australian astrophysicists, including Swinburne researchers, have announced a new worldwide discovery.