They're detecting so many of these things now. I remember reading, back when these waves were first announced to have been discovered, that they were expecting to wait YEARS before they heard anything. Yet within months of turning LIGO on for the first time, they got their first signal, and now we're detecting them with moderate frequency. Pretty neat!

 

https://www.sciencemag.org/news/202...-detectors-could-hear-murmurs-across-universe​

... a Ford versus Ferrari kind of rivalry has emerged, with scientists in the United States simply proposing bigger detectors, and researchers in Europe pursuing a more radical design.

 

https://www.syfy.com/syfywire/space...nomers-see-a-black-hole-eating-a-neutron-star

For the first time ever, astronomers have detected the scariest thing in the Universe eating the second scariest thing: A black hole devouring a neutron star.

This is simultaneously one of the coolest and most spine-chilling research results I've ever written about. A merger between these two densest types of objects in the Universe creates a colossal explosion, yet one that is utterly dark. The only way it was detected because it literally shook the fabric of spacetime.

Even better? Astronomers detected a second one just ten days later.

The orbital energy of such a system right before That Final Moment is hard to fathom. Two objects totaling several times the mass of the Sun are whirling around each other at very nearly the speed of light. That energy has to go somewhere when the two merge. Where it goes is into shaking spacetime.

When this happens, some of the mass of the system is converted directly into the energy of gravitational waves. This is an immense amount of energy. In these two new cases something like half the mass of the Sun was converted into energy. Mind you, this is done via the equation E=mc^2, and the speed of light squared is a very, very big number. The final moments lasted mere seconds, but the amount of energy created was something like 100 quintillion times the Sun's total luminosity (10^20) over the same amount of time!

Yet it was almost certainly completely dark. No light was emitted at all (no flash was seen by any telescopes, at least, and none was necessarily expected). All of the energy went into gravitational waves. Both events were roughly a billion light years away, and over that vast distance the signals weakened hugely. By the time they got here they were barely a whisper. Actually, to be honest, a whisper near the detectors would cause a far larger signal than these events did.

 

https://www.syfy.com/syfywire/space...nomers-see-a-black-hole-eating-a-neutron-star

https://twitter.com/i/web/status/1409877374049656835

​

 

A Neutron Star wanders near a Black Hole...
Neutron Star: Hey, imma just pass by real quick."

Black Hole: \*Laughs\* Are You dense? Get over here, now!

 

https://news.mit.edu/2021/hawkings-black-hole-theorem-confirm-0701

An age of insights

In 1971, Stephen Hawking proposed the area theorem, which set off a series of fundamental insights about black hole mechanics. The theorem predicts that the total area of a black hole’s event horizon — and all black holes in the universe, for that matter — should never decrease. The statement was a curious parallel of the second law of thermodynamics, which states that the entropy, or degree of disorder within an object, should also never decrease.

The similarity between the two theories suggested that black holes could behave as thermal, heat-emitting objects — a confounding proposition, as black holes by their very nature were thought to never let energy escape, or radiate. Hawking eventually squared the two ideas in 1974, showing that black holes could have entropy and emit radiation over very long timescales if their quantum effects were taken into account. This phenomenon was dubbed “Hawking radiation” and remains one of the most fundamental revelations about black holes.

“It all started with Hawking’s realization that the total horizon area in black holes can never go down,” Isi says. “The area law encapsulates a golden age in the ’70s where all these insights were being produced.”

Hawking and others have since shown that the area theorem works out mathematically, but there had been no way to check it against nature until LIGO’s first detection of gravitational waves.