Last Wednesday, a gravitational wave detection gave astronomers quite the surprise. As researchers were going about their work at the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of gravitational waves rolled in just minutes apart.
The first, labelled S190828j, was picked up by all three of LIGO’s gravitational wave detectors at 06:34 am, coordinated universal time. The second, S190828l, was measured at 06:55 – a mere 21 minutes later.
Both seemed to be the run-of-the-mill dying screams of black holes as they squish together. But here’s why it’s so surprising: astronomers wouldn’t expect to see a pair of signals in such quick succession.
In fact, this is only the second time two detections have rolled in on the same day. What’s more, at first glance they also seemed to echo from more or less the same patch of sky.
“This is a genuine “Uh, wait, what?; We’ve never seen that before…” moment in gravitational wave astronomy,” astrophysicist Robert Routledge from McGill University later tweeted, after openly speculating that it mightn’t be a mere coincidence.