Scientists discover a treasure trove of gravitational-wave signals

LIGO/Virgo announced 39 new signals, quadrupling the number of known gravitational-wave events in just six months.
By | Published: November 4, 2020 | Last updated on May 18, 2023
Stellar Graveyard LIGO/Virgo gravitational waves
The 50 gravitational wave events detected by LIGO/Virgo, including the 39 new events spotted during their third observing run, are categorized by initial mass of the progenitor objects and the mass of the resulting object.
LIGO-Virgo/Frank Elavsky, Aaron Geller/Northwestern
The Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo collaborations first detected gravitational waves in 2015. Ever since, they have continued to unveil new and exciting results as more gravitational-wave events are spotted. And on October 28, the observatories announced a surge of new gravitational wave detections from their third observing run.

The first run yielded only three events and the second run found eight. Unlike the first two runs, the recent third observing run was split into two parts. The first half stretched from April 2019 to October 2019. Since their initial 2015 detection, LIGO/Virgo detected a grand total of 50 gravitational wave events. Of those signals, 39 are new binary black hole or neutron star collisions that have not been previously announced. That’s more than three times the number of events detected in the first two runs combined.

gravitational event numbers from LIGO/Virgo
A cumulative count of gravitational wave events detected by LIGO/Virgo during the first, second, and first half of the third observing runs.
LIGO/Virgo Collaboration

Signals galore 

There are two main causes for the abundance of signals during the most recent observing run. First, the LIGO/Virgo instruments received significant improvements, which the team estimates resulted in a 60 percent improvement in the detectors’ sensitivity. On top of that, the observatories were able to operate longer without interruption, increasing the chances of picking up a signal.

With so many new signals — 50 in total, counting previous detections — astronomers have a multitude of data to tackle when it comes to black holes and neutron stars. “We’ve learned more about what nature permits,” said LIGO collaboration member Richard O’Shaughnessy in a press release. “We found more big black holes, smaller siblings of the massive event described in the summer and we found, too, that large black holes can be rapidly spinning.” With so many questions still left unanswered about these exotic objects, O’Shaughnessy suspects even more discoveries are on the horizon.

And LIGO/Virgo won’t be finished reporting new gravitational wave signals anytime soon. Results from the second half of the third run are currently being analyzed, and a fourth run is planned to begin in mid-2022. That run will also include the Kamioka Gravitational Wave Detector (KAGRA) in Japan.