The Universe is shaking: 39 new gravitational wave events added to the list - SYFY WIRE

Gravitational waves are literally ripples in the fabric of spacetime generated when extremely dense compact objects like black holes and neutron stars spiral together and merge.

The merger event shakes spacetime, hard, generating thousands of times more energy than exploding stars, but it all goes into gravitational waves that move outward at the speed of light.

This new passel includes some oddballs, including the lowest mass confirmed black hole merger, and what may have been a neutron star torn apart and eaten by a black hole.

LIGO, the Laser Interferometer Gravitational-Wave Observatory, was the first to detect them in 2015, created by a pair of massive black holes that ate each other, forming a single far more massive black hole.

Some black holes (purple) and neutron stars (orange) detected not by gravitational waves but by the light they emit are included for comparison.

The first two observing runs went well, finding 11 positively identified events, including black holes merging and even a pair of neutron stars colliding, exploding, and creating what may be a black hole.

So, two small black holes merging will generate a different waveform than two much more massive ones, or a small one and a massive one.

One of them, called GW190924_021846 (for Gravitational Wave event on 24 September 2019 and the UTC time) was from the merger of the two confirmed lowest mass black holes yet; one was 6 times the Sun's mass, and the other 9.

For example, when looking at the two black holes that merge, there's a sharp dropoff in the number of mergers where the bigger of the pair is more massive than about 40 times the Sun's mass.

The theoretical lower limit to such a black hole is about 3 times the Sun's mass.

It's possible that the Universe tends to make black holes from more massive stars, so the black hole itself is a lot more massive than the lower limit.

Interestingly, one of the papers that came with this release looked for gravitational waves coming from gamma-ray bursts, huge explosions that happen when black holes are first born.

There are black hole mergers occurring somewhere in the Universe all the time, generating a background hum of gravitational waves that, one day, we should be able to detect.