One of LIGO’s gravitational wave detectors Christian Offenberg / Alamy Stock Photo

LIGO is back at it. Having just turned back on after months of upgrades on 1 April, the Laser Interferometer Gravitational-Wave Observatory has already spotted another pair of black holes colliding.

Gravitational waves are ripples in space-time that occur whenever massive objects move, like the wake behind a boat travelling across a lake. LIGO announced the first-ever observations of gravitational waves in 2016 and has now spotted a total of 12 gravitational signatures of pairs of enormous objects smashing together.

Now that the twin detectors in Livingston, Louisiana, and Hanford, Washington, have been upgraded, we expect to see about one set of gravitational waves per week. And just one week after the detectors were turned back on, that expectation is already becoming reality with the detection of gravitational waves from a pair of merging black holes almost 5 billion light years away. LIGO made the find in collaboration with the Virgo gravitational wave observatory in Italy.


LIGO and Virgo haven’t released any information on the sizes of the two black holes. But based on the strength of the signal from so far away, they are probably relatively large like several of the earlier detections, perhaps around 30 times the mass of the sun, says astronomer Derek Fox at Pennsylvania State University. “Just being big and loud and right at the beginning of the run is exciting,” he says.

Now, these marvels of general relativity have become almost commonplace, so much so that you can sign up to be alerted to each new detection via an iPhone app. The point of the public alerts is to let astronomers around the world know where to point their telescopes for follow-up observations, says Fox.

That will come in handy during this new set of observations, which is expected to last a year or more. “This observing run is supposed to bring a real harvest of black holes and also probably a few neutron stars,” says Fox. “Some of us have been looking forward to this new era for a long time.”