Astronomers Detect Unexplained Gravitational Wave Burst Off The Shoulder Of Orion

An 'unmodeled' burst of gravitational waves has been detected, meaning the shape is not like anything we have predicted, so we do not know its cause. GiroScience/Shutterstock.com

The astronomical community is frantically scrambling to discover the source of a burst of gravitational waves that don't look like anything they have seen before – or expected to see. The hunt is disrupting other research, but it'll be a small price to pay if the event can be explained. Despite some speculation, it doesn't mean Betelgeuse is exploding.

When the LIGO/Virgo network of gravitational wave detectors was built, physicists already had a fair idea of the wave shapes black holes merging or neutron stars colliding would produce. They've since detected “chirps” that matched those expectations well. In the case of the neutron star merger, this was backed up with electromagnetic confirmation of the prediction.

Yesterday (January 14), however, LIGO registered a series of gravitational waves that looked nothing like what anyone had expected, which made it difficult to work out what was responsible.

Fortunately, unlike last year's neutron star collision, all three major detectors were online, making it possible to identify the part of the sky from which the waves came.

Astronomer and science communicator Dr Jessie Christiansen described the response.

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Telescopes worldwide have been taken off whatever they were doing to seek the source. At the time of writing, some candidates have been found, but nothing confirmed.

The redeployment of so many scientific instruments will cause a lot of valuable work to be lost, and non-astronomers may wonder why so many telescopes are required. One reason is that we need to look at a lot of different wavelengths – whatever caused this could be releasing a lot of visible light, or radio waves, or even X-rays, so it's essential to use instruments that study as many parts of the spectrum as possible.

Moreover, although the gravitational wave detectors could narrow the location down a lot, there is still a large area that needs to be searched. There is a 90 percent probability the event took place within an area of 400 square degrees, and a 50 percent chance it was within a tighter 37-square-degree area, but even the smaller area is almost 200 times the size of the full Moon. We're looking for a needle in a fairly large haystack when we don't even know what needles look like.

Professor Susan Scott of the Australian National University helps run SkyMapper, one of the best telescopes in the world for searching large areas of the sky. She told IFLScience: “At this stage, we're still trying to confirm it isn't a glitch in the instruments or something terrestrial, but it is very exciting. We've always wanted to find an unmodelled burst.”

If real, one possible explanation is a supernova burst. The search area is centered on Canis Minor, near the shoulder of Orion. That's close enough to Betelgeuse to get some people excited, given its recent fading, but it's almost certainly a coincidence. As Andy Howell of ScienceVsCinema explained, it's really no more likely to be our favorite supergiant blowing up than attack ships on fire.

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Indeed, Howell added, based on the low neutrino detection, any supernova would have to be at least 20,000 light-years away, 30 times further than Betelgeuse. On the other hand, Scott told IFLScience, supernovas in distant galaxies don't raise a ripple on LIGO, so it also couldn't be too far away, either in our galaxy or another relatively nearby. An even more exciting alternative is some new sort of cosmic event never previously detected.

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