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New Announcement on Gravitational Waves Signals a New Era

With a build-up worthy of Tom DeLonge, the European Southern Observatory (ESO) teased both the scientific and general public for weeks with promises that it was about to make an announcement that would change astronomy as we know it. The wait was over on October 16th. Was it worth the hype?

“For the first time ever, astronomers have observed both gravitational waves and light (electromagnetic radiation) from the same event, thanks to a global collaborative effort and the quick reactions of both ESO’s facilities and others around the world.”

Whoa! Whoa? What does this mean? On August 17, the Fermi Gamma-ray Space Telescope detected a seemingly normal gamma-ray burst from an unidentified source. Almost simultaneously, the Laser Interferometer Gravitational Wave Observatory (LIGO) in Washington State got an alert signaling it had received a gravitational wave signal. (It was later learned that the LIGO detector in Louisiana received the same signal but didn’t report it due to an error.)

Artist’s impression of neutron stars about to collide. (ESO)

The short burst of gamma rays was also detected by ESA’s INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL). That and the other signals helped pinpoint the source of all of the observations — a collision of neutron stars that resulted in a black hole. At that point, thanks to the astronomers’ grapevine, the news was picked up by observatories around the world and about 70 of them aimed their telescopes at the coordinates given and began picking up light, signals and photons of various wavelengths for weeks.

Composite of images of the kilonova (ESO)

“There are rare occasions when a scientist has the chance to witness a new era at its beginning, This is one such time!”

Elena Pian, an astronomer with INAF, Italy, describes the feeling she and fellow astronomers and scientists had while observing this common phenomenon on their own specialized telescopes. What they all had seen for the first time was a kilonova – a supernova caused by neutron star collision. While one had been detected in 2013 by the Hubble telescope, this was the first time so many were able to observe it and to confirm the theories that such an event can cause both light waves and gravitational waves.

Artist’s impression of the kilonova (ESO)

“The data we have so far are an amazingly close match to theory. It is a triumph for the theorists, a confirmation that the LIGO–VIRGO events are absolutely real, and an achievement for ESO to have gathered such an astonishing data set on the kilonova.”

As astronomer Stefano Covino describes it in the press release, the sound of backslapping after witnessing the kilonova must have been deafening (and painful). Another scientist and author of one of the papers detailing the discovery, Andrew Levan, described the importance of how the European Southern Observatory (ESO) managed to pull so many telescopes and instruments together so quickly.

“We have entered a new era of multi-messenger astronomy!”

Another artist’s impression of the collision (NSF/LIGO/Sonoma State University/A. Simonnet)

What next? After the astronomers sober up from the celebrations, they will begin studying the volumes of data collected and attempt to resolve some anomalies, like why the collision didn’t cause a black hole immediately and why were the gamma-rays less intense than expected. Many of the telescopes are now undergoing sensitivity upgrades so they can respond even more quickly and collect even more data when the grapevine lights up again.

In the meantime, ‘Kilonova’ would make a great name for a metal band.