Cosmic vibrations felt from merger of black holes

An artist's rendering showing two merging black holes similar to those detected by Ligo. In the latest event, a black hole 19 times the mass of the sun and another one 31 times the sun's mass, married to make a single hole.
An artist's rendering showing two merging black holes similar to those detected by Ligo. In the latest event, a black hole 19 times the mass of the sun and another one 31 times the sun's mass, married to make a single hole.PHOTO: REUTERS

Smash-up of massive black holes occurred 3 billion light years away

NEW YORK • The void is rocking and rolling with invisible cataclysms. Astronomers said on Thursday that they had felt space- time 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 three billion light years from here.

This is the third black-hole smash-up that astronomers have detected since they started keeping watch on the cosmos back in September 2015, with Ligo, the Laser Interferometer Gravitational-Wave Observatory. 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 years, the observatory has wrought twin revolutions. It validated Albert Einstein's long-standing 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 Dr 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 was published in the journal Physical Review Letters on Thursday.

"We're starting to fill in the mass spectrum of black holes in the universe," said Professor David Reitze, director of the Ligo Laboratory, a smaller group of scientists headquartered at the California Institute of Technology who built and run the observatory.

DEEP INTO TIME AND SPACE

In this case, we're exploring approximately three billion light years away!

NATIONAL SCIENCE FOUNDATION DIRECTOR FRANCE CORDOVA, on the latest Ligo event published in the journal Physical Review Letters on Thursday.

The National Science Foundation (NSF), which poured US$1 billion (S$1.4 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," Dr France Cordova, the foundation's director, said in a statement. "In this case, we're exploring approximately three billion light years away!"

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 three billion years, 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. 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 Prof Reitze said: "Once again, Einstein triumphs."

NYTIMES

A version of this article appeared in the print edition of The Straits Times on June 03, 2017, with the headline 'Cosmic vibrations felt from merger of black holes'. Print Edition | Subscribe