Scientists confirm gravitational waves

Gravitational waves from space have been detected for the first time, with help from an Edinburgh scientist.

The fundamental discovery by an international team confirms part of Albert Einstein’s general theory of relativity.

Gravitational waves are ripples of energy in space, which can be emitted by neutron stars or caused by high-energy mergers between pairs of black holes.

Their confirmation gives physicists valuable insight into the universe, and opens up new avenues for astronomy and to test Einstein’s theory of general relativity.

It could lead to important insights about the evolution of stars, supernovae, gamma-ray bursts, neutron stars and black holes.

Complex analysis

Gravitational waves, originating from the collision of two black holes, were identified by two independent detectors in the US.

They were verified by a team of scientists, including a researcher from Edinburgh’s School of Mathematics, after many months of analysis.

The waves detected in the study were formed when two black holes, each around 30 times the mass of the Sun and more than 1,000 light years from Earth, coalesced to form a single, more massive black hole.

The phenomenon confirms Einstein’s prediction of the existence of gravitational waves some 100 years after it was posited.

Sophisticated detectors

The waves were detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) collaboration using detectors in Louisiana and Washington.

Each detector comprises two four-kilometre long tubes, in an L-shape. A laser beam sent down each of the tubes very precisely monitors the distance between mirrors at each end.

According to Einstein’s theory, the distance between the mirrors will change by a tiny amount when a gravitational wave passes by, with one arm getting longer while the other gets shorter.

In analysing the data, scientists look for differences in the arm lengths that vary in a particular way.

Verified results

Independent observations are needed to verify the gravitational waves, and to determine the direction from which they are coming, which is why two separate detectors are used.

The LIGO consortium of nearly 1,000 scientists from 16 countries used supercomputers to calculate and validate the data.

Their study is accepted for publication in the journal Physical Review Letters.

The project is funded by the UK’s Science and Technology Facilities Council (STFC), the US National Science Foundation (NSF), the Max Planck Society of Germany, and the Australian Research Council (ARC).

Detector upgrade

In future, the LIGO detectors will be upgraded to further increase their sensitivity to gravitational waves, and enabling more distant events to be measured.

An additional detector in Italy, Virgo, will come online in the next two years and there are plans for a detector in Japan, KAGRA, and a third LIGO detector in India by the end of this decade.

The addition of extra detectors to the network will improve sensitivity and the precision with which the direction to individual sources can be determined.

It is satisfying to see validation of all the work that has gone into this project so far. These findings create new opportunities for more detailed research into the phenomenon of gravitational waves. They also offer the exciting prospect of using gravitational waves as a tool to better understand the properties of exotic astrophysical systems, like black hole binaries.

Dr Jonathan GairSchool of Mathematics