Colliding stars reveal their gravitational wave secrets


The collision, which was later identified as a neutron star merger, was observed August 17 by the Laser Interferometer Gravitational-Wave Observatory, or LIGO, in the United States and the Virgo detector in Italy. Some 130 light years away, the two stars began an unstoppable dance, drawing closer and closer to each other, until they were spinning around each other more than 500 times per second, distorting space and time as they did so.

Not only is the first time we've spotted a neutron star merger, but it's also the first time gravitational waves have been detected from anything other than black hole mergers, which are invisible to telescopes. It registered ripples in space-time formed from the collision of two black holes. The explosion of neutron stars, which are made nearly entirely of neutrons, was detected by multiple telescopes across the electromagnetic spectrum, from gamma rays and visible light to radio waves.

By observing a fleeting star-like object in the sky in August, they've learned a lot of new things about the universe worth clinking glasses over.

Astrophysicists managed catch the first glimpse ever of a unique astronomical event. If they'd been better aligned, the intensity of the jet's light would have obscured the kilonova's radioactive blaze. However, in the classical Sherlock Holmes style, "why the dog did not bark", the non-detection of gamma rays by AstroSAT and the non-detection of gravitational waves by the third detector, Virgo, at Europe meant they were in the blind spots.

"This is a revolution in astronomy, of having thousands of astronomers focus on one source for weeks and having this collaboration unravel in seconds, in hours, then days, and weeks". This confirmed that "maybe half, maybe more, of the heavy elements in the Universe are actually produced by this kind of collision", said physicist Patrick Sutton, a member of LIGO.

The first gravitational wave was detected two years ago. For the past century, astronomers have been trying to figure out how to detect the ripples, which were predicted by Albert Einstein in his theory of general relativity. It appeared that the objects were not as massive as binary black holes - objects that LIGO and Virgo have previously detected.

The combination of gravitational-wave and gamma-ray observations allowed the position of the cosmic explosion to be pinpointed to less than 30 square degrees on the sky - or about 100 times the size of the full moon. LIGO includes two instruments, in Livingston, Louisiana, and in Hanford, Washington.

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Interestingly, the August 17 event was almost missed because the gravitational wave signal was not immediately evident in Livingston data due to a burst of noise.

Many Indian scientists were part of the gravitational wave detection.

"Now, astronomers won't just look at the light from an object, as we've done for hundreds of years, but also listen to it", Tanvir said. At almost the same time, the Gamma-ray Burst Monitor on NASA's Fermi space telescope detected a burst of gamma rays.

Scientists shared evidence of a massive and violent collision between two dead stars.

In the meantime, the astronomers thought that Virgo observatory had missed the signal, as it was not visible in the observatory's data. Scientists then were able to find the galaxy where the occurrence took place, which they said was relatively nearby - within 250 million light-years from Earth. "Gravitational-wave astronomy offers new opportunities to understand the properties of neutron stars in ways that just can't be achieved with electromagnetic astronomy alone". "This ushers in the era of multi-messenger astronomy, it is like being able to see and hear for the first time". "There's nothing like the feeling knowing you're one of the first people in the world to see a new phenomenon". "These neutron star mergers are believed to be one of the most important sites where heavy elements are made".

Neutron stars, the densest in the universe and measuring just 10km across, are found alone but also in pairs orbiting each other.

Kilonova "flash" seen within one hour Smartt explained the GW signal came from the southern hemisphere, meaning that ESO's suite of large telescopes in Chile were ideally placed to search for any "transient" optical signals relating to the GW and GRB events. While theories have existed for a long time regarding what might occur during such an event, we've now managed to learn quite a bit - including, as it turns out, that the marriage of two neutron stars results in an explosion of gold, platinum, and other heavy metals.