Gravitational Waves From Black Holes Detected For The Third Time


Scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO) confirm that the organization's twin observatories in Washington and Louisiana detected gravitational waves for the third time on Jan. 4.

The gravitational wave came from the collision of black holes that are 32 and 19 times the mass of our sun located about 3 billion light-years away. The third detection has been named GW170104.

Nearly Missed Third Detection

The LIGO facilities were offline for most of 2016 to receive upgrades but resumed operations on Nov. 30, 2016. Just a month into the second observing run, LIGO's interferometer in Washington picked up a wave that was also detected by the Louisiana detector a mere 3 milliseconds later.

Scientists were quick to crunch numbers to determine whether the detected wave was a fluke or the real thing and, after much effort, confirmed that the little shiver the interferometers detected is a genuine gravitational wave from the collision of two black holes located farther than the first two detections.

In fact, LIGO scientists calculated that they are 99.997 percent certain that the detected shiver is a gravitational wave. They further computed that the chances both interferometers would detect a random (non-gravitational wave) burst at the same time will only likely happen once in 70,000 years.

Detecting a third wave is not the only thing LIGO scientists are excited about because GW170104, aside from further confirming Einstein's theory, also brought new knowledge about the way black holes spin.

"We have an indication that at least one of the two spins is not aligned with the orbital angular momentum," Pennsylvania State University cosmologist B.S. Sathyaprakash revealed.

New Knowledge On Black Holes

Most people already know that, just like tornadoes, black holes can spin clockwise or counterclockwise and tilt as they do so, but previously detected binary pairs of black holes usually have aligned spins. That is, a pair of black holes may spin in different directions, but they usually follow the same orbital axis within its system since they are born together. The newly discovered and merged black holes, however, appear to be misaligned, which means they were not born as a pair but rather formed separately within the same dense star cluster.

"We're starting to gather real statistics on binary black hole systems ... in the future, we can further narrow this down," Caltech scientist Keita Kawabe said. Kawabe is also a coauthor in the research.

Einstein's general theory of relativity was further validated in the latest findings because the merging of the two black holes offered evidence that gravitational waves did not experience dispersion.

"It looks like Einstein was right ... We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence," LIGO Scientific Collaboration deputy spokesperson Laura Cadonati expressed.

Watch the simulation below.

Advancing Gravitational Wave Detection

Scientists would benefit greatly if more observatories know where to look when LIGO detects gravitational waves, but as of now, the organization can only point researchers to a general direction.

This could all change, however, when the Virgo observatory in Italy goes online in summer because three observatories could potentially narrow down the location of the source of gravitational waves. If that is still insufficient, however, Japan is also slated to begin operation of its interferometer as early as 2018.

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