gravity

JAKARTA – International scientists have for the first time discovered evidence of a long-theorized gravitational waveform that creates a rumbling “background hum” throughout the universe, observing faint ripples caused by the motion of black holes gently stretching and compressing everything in the universe.

Last Wednesday, they reported hearing what are called low-frequency gravitational waves, changes in the structure of the universe due to the movement and collision of massive objects in space.

“This is really the first time we have evidence of the large-scale motion of everything in the universe,” said Maura McLaughlin, co-director of NANOGrav, an international research collaboration that published its results in ‘The Astrophysical Journal Letters‘, as reported Daily Sabah from AP June 29.

It is known, Einstein once said, that when very heavy objects move through space, they create ripples that spread through the structure. Scientists sometimes liken these ripples to the background music of the universe.

In 2015, scientists used an experiment called LIGO to detect gravitational waves for the first time, showing Einstein was right.

But so far, the method has only been able to capture waves at high frequencies, explains NANOGrav member Chiara Mingarelli, an astrophysicist at Yale University.

The rapid “chirps” stem from certain moments when relatively small black holes and dead stars collide with each other, Mingarelli said.

In the latest research, scientists are looking for waves at much lower frequencies. These slow ripples can take years or even decades to swirl up and down, and may originate from some of the largest objects in our universe.

The background noise they found was “louder” than some scientists had thought, Mingarelli said.

This could mean there are more, or larger, black hole mergers occurring in space than previously thought, or point to other sources of gravitational waves that could challenge our understanding of the universe.

Space illustration. (Wikimedia Commons/Fearedlion123)

Separately, Szabolcs Marka, an astrophysicist at Columbia University who was not involved in the research, said galaxies throughout the universe are constantly colliding and merging together. As this happens, scientists believe the enormous black holes at the center of these galaxies also come together and lock in a dance before eventually collapsing into one another.

Black holes send out gravitational waves as they rotate in these pairs, which are known as binaries.

“Supermassive black hole binaries, slowly and quietly orbiting each other, are the tenor and bass of a cosmic opera,” explains Marka.

No instrument on Earth can pick up on the ripples from these giants. So “we had to build a detector that was roughly the size of a galaxy,” says NANOGrav researcher Michael Lam of the SETI Institute.

The results released this week include 15 years of data from NANOGrav, which has used telescopes across North America to search for the waves. Other gravitational wave hunting teams around the world are also publishing research, including in Europe, India, China and Australia.

Scientists pointed their telescopes at a dead star called a pulsar, which sends out flashes of radio waves as it swirls through space like a beacon.

These bursts are so regular that scientists know exactly when radio waves should arrive on our planet — “like a perfectly regular clock ticking far out in outer space,” says NANOGrav member Sarah Vigeland, an astrophysicist at the University of Wisconsin-Milwaukee.

But, as gravitational waves bend the fabric of spacetime, they actually change the distance between Earth and this pulsar, throwing off those steady beats.

By analyzing small changes in the beat rate of different pulsars, scientists can tell that gravitational waves are passing through them.

The NANOGrav team monitored 68 pulsars in the sky using the Green Bank Telescope in West Virginia, the Arecibo telescope in Puerto Rico, and the Very Large Array in New Mexico. Another team found similar evidence from dozens of other pulsars, which they monitored with telescopes around the world.

However, Marc Kamionkowski, an astrophysicist at Johns Hopkins University who was not involved in the study, said this method has not been able to trace exactly where these low-frequency waves come from.

Researchers hope that continuing to study these types of gravitational waves can help learn more about the largest objects in the universe, opening new doors to “cosmic archeology” that can trace the history of black holes and the merging of galaxies around us, Marka said.

Tags: international scientific research space research astronomy

2023-07-01 15:12:48
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