Far out cosmology: finding gravitational wave hums (Introduction)

by David Turell , Thursday, June 29, 2023, 16:26 (303 days ago) @ David Turell

Latest research:

https://www.science.org/content/article/long-sought-hum-of-gravitational-waves-from-gia...

"By turning networks of dead stars into galaxy-size gravitational wave detectors, radio astronomers have tuned into the slowly undulating swells in spacetime thought to arise from pairs of supermassive black holes (SMBHs) that are about to collide.

"In a simultaneous announcement today, five separate international teams said that after nearly 20 years of effort they had found evidence for these gravitational waves. They are far longer than the waves first captured by ground-based detectors in 2015, which emanate from collisions of star-size objects. The findings not only open up a new window in gravitational wave astronomy, but will also help researchers answer questions about the origin and evolution of SMBHs, objects that sit at the center of galaxies and weigh as much as billions of Suns. The results could even uncover hints of new physics.

"The new results rely on millisecond pulsars, highly magnetized stellar remnants that emit beams of radiation as they spin as fast as 1000 times per second. Their lighthouse-like radio signals sweep past our planet with a regularity that rivals an atomic clock. Should a passing gravitational wave intrude anywhere along the path between Earth and the pulsar, it will stretch and squash the fabric of space—and cause small variations in the timing of the flashes. “Those ultraprecise signals will arrive a little bit early, and then a little bit late,” says Chiara Mingarelli, an astrophysicist at Yale University and a member of the North American Nanohertz Observatory for Gravitational Waves. NANOGrav is one of the five international pulsar timing arrays (PTAs), which draw on data from a dozen radio telescopes around the world to monitor dozens of the beacons for evidence of the waves.

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"The background signal is stronger than expected, implying that this population of imminently merging SMBHs numbers in the hundreds of thousands, perhaps even millions. It could also mean the SMBHs are either bigger or merging more quickly than astronomers previously predicted—a possibility consistent with observations from NASA’s JWST space telescope hinting that galaxies grew larger and faster in the early universe than once thought.

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"Having heard the cosmic hum, the teams now want to listen more closely, digging deeper into their data sets to find out what else they might learn. “We’re not even close to the end of the story,” Hessels says. “It’s a game of dedication and patience.'”

Comment: it takes dedication, perseverance, and money to reach this type of result. All because we are so curious. One day we may be able to tell dhw why the universe is so big.