They detect the ‘clamor’ of gravitational waves in the universe

2023-06-29 13:10:07

You can’t see or feel it, but everything around you – including your own body – is slowly expanding and shrinking. It is about the strange effect of gravitational waves that traverse our galaxy and that distort space-time. According to a new study published in The Astrophysical Journal Letters.

The authors belong to North American Nanohertz Observatory for Gravitational Waves (NANOGrav)an international collaboration of more than 70 institutions, mainly from the USA, with funding from the National Science Foundation (NSF) of that country.

For the study, the team performed an analysis of known glowing stars. like pulsars of millisecondswhich rotate hundreds of times per second and emit radio pulses like cosmic clock ticks of great precision.

cosmic clocks

Thus they discovered what appeared to be variations in the “tic-tac rhythm” of these pulsars, comparing data from more than 60 of these objects observed in our galaxy with radio telescopes over 15 years.

Their analysis shows that the variations are caused by low frequency gravitational waves that distort the ‘fabric’ of physical reality known as space time.

According to the NANOGrav team’s conclusions, spatial distortion caused by gravitational waves creates the appearance that the frequency of radio signals from pulsars is changing.

Actually, it’s the stretching and compression of space between Earth and pulsars causing their radio pulses to reach Earth billionths of a second earlier or later than expected.

The results are the first evidence of the gravitational wave background, a kind of spacetime warp soup that invades the entire universe and that scientists have long predicted that it exists.

“The NANOGrav team has created, in essence, a galactic scale detector that reveals the gravitational waves that permeate our universe”, says the director of the NSF, Sethuraman Panchanathan.

The first proof of the background of gravitational waves is presented, a kind of ‘soup’ of space-time distortions that invades the entire universe

Gravitational waves were first predicted by Albert Einstein in 1916. They would not be confirmed until 2015, when the Laser Interferometer Gravitational Wave Observatory (LIGO) detected ripples in space-time traversing the Earth.

Although the source of those gravitational ripples was a collision of two black holes distantthe resulting spatial distortion that LIGO detected was smaller than the nucleus of an atom.

By comparison, the apparent time displacement of pulsars as measured by the NANOGrav team is a few hundred billion seconds and represents a bending of space-time between the Earth and the pulsars of the length of a football field.

Gravitational waves coming from a pair of closely orbiting black holes. / Keyi “Onyx” Li/US/NSF

Those space-time distortions were caused by gravitational waves so immense that the distance between two crests is two to ten light-yearsor about nine to 90 trillion kilometers.

“These are by far the strongest gravitational waves known,” he says. Maura McLaughlinan astrophysicist at West Virginia University and co-director of NANOgrav, “and detecting such gigantic gravitational waves requires an equally massive detector, and patience.”

Using 15 years of astronomical data recorded by radio telescopes at NSF-funded observatories—including the Green Bank Observatory in West Virginia, the Very Large Array in Socorro, New Mexico, and the Arecibo Observatory in Puerto Rico—the team NANOGrav created a “detector” of 67 pulsars scattered across the sky and compared the ticking frequency of pairs of those pulsars.

The Very Large Array in New Mexico is one of the radio telescopes that collected data to detect the gravitational wave background of the universe. / NRAO/AUI/NSF

Through a sophisticated analysis of the data, they deduced the presence of the gravitational wave background that caused the the distortion of spacethus explaining the apparent timing changes of the pulsars.

Source in colossal supermassive black holes

“This is the first proof of the existence of gravitational waves at these low frequencies,” he says. Stephen Tayloran astrophysicist at Vanderbilt University, chair of the NANOGrav collaboration and co-director of the research, who explains: “The likely source of these waves are distant pairs of ultimate black holes in close orbit.

These are by far the strongest gravitational waves known.

Maura McLaughlin, co-director of NANOgrav

The team’s results provide new insights into how galaxies evolve and how supermassive black holes grow and merge. The pervasive distortion of space-time revealed by their findings implies that pairs of extremely massive black holes may be equally spread throughout the universeperhaps in the hundreds of thousands or even millions.

Over time, the NANOGrav team hopes to be able to identify particular supermassive black hole pairs by tracking the gravitational waves they emit. They might even discover gravitational wave signals from the early universe.

“Our first data told us that we were hearing something, but now we know that it is the music of the gravitational universe“, Explain Xavier Siemensco-director of NANOGrav and an astrophysicist at Oregon State University (USA), and anticipates: “As we continue to listen, individual instruments will appear in this cosmic orchestra.”

Fuente: NSF

Rights: Creative Commons.