Black holes 3 billion light years away yield 3rd gravitational wave discovery

The void is rocking and rolling with invisible cataclysms.

Astronomers said Thursday that they had felt spacetime vibrations known as gravitational waves from the merger of a pair of mammoth black holes resulting in a pit of infinitely deep darkness weighing as much as 49 suns, some 3 billion light-years from here.

This is the third blackhole smashup that astronomers have detected since they started keeping watch on the cosmos back in September 2015, with LIGO, the Laser Interferometer Gravitational-Wave Observatory — and it is much farther than the previous two discoveries. All of them are more massive than the black holes that astronomers had previously identified as the remnants of dead stars.

In less than two short years, the observatory has wrought twin revolutions. It validated Einstein’s longstanding prediction that space-time can shake like a bowlful of jelly when massive objects swing their weight around, and it has put astronomers on intimate terms with the most extreme objects in his cosmic zoo and the ones so far doing the shaking: massive black holes.

“We are moving in a substantial way away from novelty towards where we can seriously say we are developing black-hole astronomy,” said David Shoemaker, a physicist at the Massachusetts Institute of Technology and spokesman for the LIGO Scientific Collaboration, an international network of about 1,000 astronomers and physicists who use the LIGO data. They and a similar European group named Virgo are collectively the 1,300 authors of a report on the most recent event that will be published in the journal Physical Review Letters on Thursday.

“It clearly establishes a new population of black holes that were not known before LIGO discovered them,” said LIGO scientific collaboration member Bangalore Sathyaprakash of Penn State and Cardiff universities.

“We’re starting to fill in the mass spectrum of black holes in the universe,” said David Reitze, director of the LIGO Laboratory, a smaller group of scientists headquartered at Caltech who built and run the observatory.

The National Science Foundation, which poured $1 billion into LIGO over 40 years, responded with pride. “This is exactly what we hoped for from NSF’s investment in LIGO: taking us deeper into time and space in ways we couldn’t do before the detection of gravitational waves,” Frances Cordova, the foundation’s director, said in a statement.

In the latest LIGO event, a black hole 19 times the mass of the sun and another black hole 31 times the sun’s mass, married to make a single hole of 49 solar masses. During the last frantic moments of the merger, they were shedding more energy in the form of gravitational waves than all the stars in the observable universe.

After a journey lasting 3 billion years, that is to say, a quarter of the age of the universe, those waves started jiggling LIGO’s mirrors back and forth by a fraction of an atomic diameter 20 times a second. The pitch rose to 180 cycles per second in about a tenth of a second before cutting off.

The new signal, called GW170104, was picked up in the early morning hours of Jan. 4 by the twin L-shaped detectors in Hanford, Wash., and Livingston, La.

Upon further analysis it proved to be a perfect chirp, as predicted by Einstein’s equations.

Because of the merger’s great distance, the LIGO scientists were able to verify that different frequencies of gravity waves all travel at the same speed, presumably the speed of light. As Mr. Reitze said, “Once again Einstein triumphs.”

The burning question now is: Where did such massive black holes come from?

One possibility is that they were born that way, from a pair of massive stars orbiting each other that evolved, died, blew up and then collapsed again into black holes — all without either star getting kicked out of the system during one of those episodes of stellar violence.

Another idea is that two pre-existing black holes came together by chance and captured each other gravitationally in some crowded part of the galaxy, such as near the center, where black holes might naturally collect.

Astronomers won’t say which explanation is preferred, pending more data, but what Mr. Reitze calls a “tantalizing hint” has emerged from analysis of the Jan. 4 chirp — which is being called GW170104 — namely how the blackholes were spinning.

If the stars that gave rise to these black holes had been lifting and evolving together in a binary system, their spins should be aligned, spinning on parallel axes like a pair of gold medal skating dancers at the Olympics, Mr. Reitze explained.

Examination of the January chirp, Mr. Reitze said, gives hints that the spins of the black holes were not aligned, complicating the last motions of their mating dance.