New York — Scientists have observed for the first time light waves caused by the motion of a black hole that is slowly stretching and squeezing everything in the universe.
They reported Wednesday that they were able to “hear” what are called low-frequency gravitational waves — changes in the structure of the universe that are produced by massive objects moving around and colliding in space.
“This is really the first time that we have evidence of such large-scale motion of everything in the universe,” said Maura McLaughlin, co-director of NANOGrav, the research collaboration that published the results in The Astrophysical Journal Letters.
Einstein predicted that when really massive objects move through spacetime – the fabric of our universe – they create waves that propagate through that fabric. Scientists sometimes compare these waves to the background music of the universe.
In 2015, scientists used an experiment called LIGO to detect gravitational waves for the first time and showed that Einstein was right. But so far, these methods have only been able to capture waves at high frequencies, explained NANOGrav member Chiara Mingarelli, an astrophysicist at Yale University.
Mingarelli said those quick “chirps” come from specific moments when relatively small black holes and dead stars collide with each other.
In the latest research, scientists were searching for waves at very low frequencies. These slow waves can take years or even decades to cycle up and down, and likely come from some of the most massive objects in our universe: supermassive black holes billions of times the mass of our Sun.
Galaxies in the universe are constantly colliding and merging together. As this happens, scientists believe the supermassive black holes at the centers of these galaxies also come together and lock themselves in a dance before eventually collapsing into each other, says an astrophysicist at Columbia University. explained physicist Szabolcs Marka, who was not involved in the research.
Black holes send out gravitational waves when they orbit in these pairs, which are known as binaries.
“Supermassive black hole binaries, slowly and peacefully orbiting each other, are the tenor and bass of the cosmic opera,” Marca said.
No instrument on Earth could catch the waves of these giants. “We had to build a detector that was roughly the size of the Milky Way,” said NANOGrav researcher Michael Lamm of the SETI Institute.
The results, released this week, include 15 years of data from NANOGrav, which is using telescopes across North America to search for the waves. Other teams of gravitational wave hunters around the world also published studies, including in Europe, India, China and Australia.
Scientists pointed telescopes at dead stars called pulsars, which emit flashes of radio waves as they roam space like lighthouses.
These bursts are so regular that scientists know exactly when the radio waves are about to arrive on our planet—”like a perfectly regular clock ticking far out in space,” a University of Wisconsin-Milwaukee astrophysicist said physicist, NANOGrav member Sarah Vigeland. , But as gravitational waves distort the fabric of space-time, they actually change the distance between Earth and these pulsars, throwing off that steady pulsation.
By analyzing small changes in tick rates in different pulsars – some pulses arriving slightly earlier and others late – scientists could tell that gravitational waves were passing through.
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. Other teams found similar evidence from dozens of other pulsars monitored with telescopes around the world.
So far, this method hasn’t been able to detect where these low-frequency waves are actually coming from, said Mark Kamionkowski, an astrophysicist at Johns Hopkins University who was not involved in the research.
Instead, it’s manifesting the constant hum that’s all around us — like when you’re standing in the middle of a party, “You’ll hear all these people talking, but you won’t hear anything in particular, Kamionkowski said.
Mingarelli said the background noise they found is “louder” than some scientists expected. This could mean that black holes are merging further out in space, or larger, than we thought – or could point to other sources of gravitational waves that may challenge our understanding of the universe.
Researchers hope that continuing to study these types of gravitational waves can help us learn more about the largest objects in our universe. This could open new doors for “cosmic archeology” that can track the history of merging black holes and galaxies around us, Marca said.
“We’re starting to open up this new window on the universe,” Vigeland said.
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