UCD astronomers in landmark discovery

UCD astronomers landmark discovery
Gravitational Wave Source

International teams of researchers, including astronomers from the Space Science Group in University College Dublin’s (UCD) School of Physics, have announced the discovery of light associated with a gravitational wave source.

According to Professor Lorraine Hanlon, UCD School of Physics, the discovery vindicates the involvement of Irish astronomers in such “international consortia”.

The Advanced LIGO and Advanced VIRGO teams reported the detection of a gravitational wave source (GW170817), consistent with the merger of two neutron stars, for the first time.

Gamma-rays, followed by optical and infrared radiation, were also detected from the same region of the sky.

Professor Hanlon, said: “Maintaining access to the gamma-ray sky with more sensitive facilities will be essential to progress the emerging field of multi-messenger astrophysics that has been revealed by these stunning discoveries announced today.

Momentum

“These discoveries give momentum to the case for supporting Irish astronomers’ participation in international consortia that operate at the frontier of fundamental research, on a scale that cannot be achieved by any single institute or country.”

Gravitational waves, ripples in the fabric of spacetime, were first anticipated by Albert Einstein a century ago in his general theory of relativity.

This theory predicts that the presence of a mass causes a curvature in spacetime and that when massive objects, such as black holes, merge, this curvature can be altered, sending ripples, or gravitational waves, out across the Universe. By the time these ripples reach Earth, they are however almost imperceptible.

In September 2015 gravitational waves were observed for the first time after scientists from over 20 countries collaborated to develop a detector, the Advanced Laser Interferometer Gravitational Wave Observatory (aLIGO), located in the USA, that was sensitive enough to confirm their existence.

The 2017 Nobel Prize in Physics was recently awarded to Kip Thorne, Barry Barish and Rainer Weiss for this discovery.

Working hard

Speaking at University College Dublin Dr Morgan Fraser, said: “Since the first discovery of gravitational waves two-years ago, astronomers have been working hard to find their counterparts at optical wavelengths.

“Now with today’s announcement we are seeing the dawn of a new field of ‘multimessenger astronomy’, where detections of transients across the electromagnetic spectrum, along with gravitational waves, are opening up a whole new window on the Universe.”

He added: “The data from ESO telescopes also allowed the team to identify possible signatures of Cesium and Tellurium in the debris of the remains after the neutron stars merged. Finding these elements has been a crucial discovery in understanding the source of the heavy elements in the Universe.”

“We can now say, with some confidence, that Cesium and Tellurium on Earth, which are for example used in atomic clocks, electronics and solar panels, would have been produced in a merger of two neutron stars in our own galaxy, more than 4.5 billion years ago.”

Since the first gravitational wave detection, caused by a collision between two black holes 1.3 billion years ago, aLIGO, in conjunction with the Advanced VIRGO (aVIRGO) detector, located in Pisa, Italy, has observed gravitational waves from several other sources.

Black holes

In all cases up to now, the gravitational waves detected were from the merger of black holes about 30 times the mass of our Sun and, despite searches by astronomers, no counterparts were found by telescopes sensitive to gamma-rays, X-rays, optical, infra-red or radio waves.

On 17 August 2017 gravitational waves from the merger of two compact stellar remnants, called neutron stars, were detected by two out of three aLIGO/aVIRGO systems.

Less than two seconds later, gamma-rays were detected from the same region of the sky by NASA’s Fermi Gamma-ray Space Telescope and ESA’s INTEGRAL satellite. Both satellites detected a gamma-ray burst, which proves that some gamma-ray bursts are caused by the merger of neutron stars.

This observation is of immense significance to astrophysics and may allow scientists to explain the unknown origin of some of the heavy metals found on Earth.


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