All you need to know about Gravitational waves detected by LIGO scientists for the second time

Confirming Albert Einstein’s theory of general relativity once again, scientists have directly detected gravitational waves for the second time. The gravitational waves were formed by the collision of two black holes 1.4 billion light years away. Here are the facts you should know about the discovery of second gravitational waves:

1. The twin Laser Interferometer Gravitational-wave Observatory (LIGO) interferometers in the US was used by the scientists to detect the gravitational waves – ripples through the fabric of the space-time continuum.

2. Both detectors, situated more than 3,000 kilometres apart, picked up a very faint signal amid the surrounding noise on December 26 last year. 

3. LIGO detected the first gravitational waves on February 11 this year. The first detection produced a clear peak in the data, this second signal was far subtler, generating a shallower waveform that was almost buried in the data, researchers said.

4. The team used advanced data analysis techniques and determined that the waveform indeed signalled a gravitational wave. 

5. The collision of two black holes, 14.2 and 7.5 times the mass of the Sun, gave birth to the gravitational wave, scientists calculated.

6. The signal picked up by LIGO’s detectors encompasses the final moments before the black holes merged.For roughly the final second, while the signal was detectable, the black holes spun around each other 55 times, approaching half the speed of light, before merging in a collision that released a huge amount of energy in the form of gravitational waves, equivalent to the mass of the Sun.

7. This cataclysm, occurring 1.4 billion years ago, produced a more massive spinning black hole that is 20.8 times the mass of the Sun. This second detection of gravitational waves, which once again confirms Einstein’s theory of general relativity, successfully tested LIGO’s ability to detect incredibly subtle gravitational signals.

8. LIGO’s two interferometers, each four kilometres long, are designed in such a way that each detector should stretch by an infinitesimal amount if a gravitational wave were to pass through.

9. On September 14 last year, the detectors picked up the very first signal of a gravitational wave, which stretched each detector by as little as a fraction of a proton’s diameter. Just four months later, LIGO recorded a second signal, which stretched the detectors by an even smaller amount.

10. In its first four months, the Advanced LIGO detectors have already detected two signals of gravitational waves, produced by the collision of two very different binary black hole systems. The research was published in the journal Physical Review Letters. 

(With inputs from PTI)