Gravitational waves detected for a second (and maybe third) time

Three months after the detection of the first ever gravitational waves, scientists were once again able to record the signal of a space-time distortion, according to new research presented Wednesday during the annual meeting of the American Astronomical Society.

The discovery, which was also detailed in a paper published in the latest edition of the journal Physical Review Letters, once again involved detecting a minute gravitational wave signal given off by a pair of black holes close to the point of merging – a phenomenon known as coalescence, the French National Centre for Scientific Research (CNRS) revealed in a statement.

The signal was detected on December 26 by scientists from the US-based LIGO and the Italian-based Virgo collaborations, confirming that these phenomenon are more frequent than experts previously believed and increasing the odds that additional gravitational waves will be detected once the two now-upgraded observatories resume operations later on this year.

While the signal for the second set of gravitational waves is said to have been weaker than the original one, but nonetheless has been confirmed with a confidence level exceeding 99.99999%, the CNRS said. Furthermore, additional analysis of the LIGO data has revealed a possible third detection of coalescing black holes on October 2, 2015, but scientists note that this event carries with it a lower degree of certainty than the other two.

Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained. Credit: NASA

Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained. Credit: NASA

Findings will help scientists determine the origins of binary black holes

The discovery will help scientists better understand pairs of black holes, which are objects that are so dense that neither matter nor light can escape them, the research center explained. Black holes are the final evolutionary stage of the most massive stars, and in some cases, pairs of these phenomena from, orbiting one another while releasing energy as gravitational waves.

Eventually, the process suddenly accelerates and the two black holes merge into one, which was the case with the black holes that were the source of gravitational waves detected last December. Observations of these two objects enabled researchers to determine that they had masses between 8 and 14 times that of the sun, while the black holes involved in the original observations back in September 2015 had solar masses of 29 and 36, according to the CNRS.

As the two black holes became lighter, they actually began to move towards each other at slower speeds, meaning that the signal detected by LIGO and Virgo lasted much longer than the original one – several seconds compared to less than one-half second. This enabled scientists to conduct a different and complementary series of tests than were performed during the September event.

December’s detection, which took place 1.4 billion light years from Earth, and other events like it could ultimately make it possible for researchers to determine the origin of binary black holes, and to determine if they were twin stars that both just happened to turn into black holes or if the gravitational pull of one attracted and captured the other. To determine this, experts will need to collect additional samples, and they are hopeful that the aforementioned upgrades to LIGO and Virgo will make that possible after the go back online in the fall of 2016.


Image credit: Ossokine and A. Buonanno, Max Planck Institute for Gravitational Physics, and the Simulating eXtreme Spacetime (SXS) project