Though long hypothesized, the newly detected gravitational wave background was never previously audible.
- Scientists can now “hear” gravitational waves that are created by Black Holes.
- The cosmic symphony reverberating through the universe is now accessible, thanks to a 15-year observation of pulsars by the NANOGrav team.
- Scientists have detected the harmonious ensemble of gravitational waves, the ripples in space-time, uncovering sounds far louder than anticipated for the first time.
How to Hear Gravitational Waves Created by Black Holes
The breakthrough comes from the diligent work of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) scientists. Studying pulsars, stellar metronomes, they have caught the most potent gravitational waves recorded, boasting about a million times the energy of the fleeting gravitational waves detected by LIGO and Virgo experiments.
Cosmic Cataclysms Spur Gravitational Chorus
Supermassive black hole pairs spiraling towards catastrophic collisions across the cosmos are the suspected maestros of this powerful gravitational symphony, according to recent papers by NANOGrav researchers published in The Astrophysical Journal Letters.
Chiara Mingarelli, a NANOGrav scientist, likens this phenomenon to a choir where each supermassive black hole pair sings at different frequencies. Mingarelli, who contributed to the study, states this is the debut evidence for the gravitational wave background, ushering a new epoch in observing the cosmos.
For particularly regular pulsars, those pulses are as regular as, or more regular than, our best atomic clocks! Now a gravitational wave arrives. You might have seen animations of what gravitational waves do. If you make a circle out of freely floating particles, then a 4/
— Markus Pössel (@mpoessel) June 25, 2023
Gravitational Background Wave – A Treasure Trove of Insights
Though long hypothesized, the newly detected gravitational wave background was never previously audible. Its discovery unveils invaluable knowledge about longstanding cosmic enigmas, such as the fate of supermassive black hole pairs and the frequency of galactic mergers.
For the time being, NANOGrav can only assess the overall gravitational wave background rather than the individual cosmic singers. But even this comprehensive measure has revealed surprises. The gravitational wave background’s sound intensity is nearly double of what was anticipated, possibly hinting at larger and more plentiful supermassive black holes, or even new sources of gravitational waves.
A Decades-Long Gravitational Ballet
The NANOGrav team had to look to the stars to detect these colossal waves that differ from any previously recorded, resulting from their ultra-low-frequency nature. Using pulsars as their guide, scientists were able to detect these gravitational waves due to their influence on the precise timing of radio waves from pulsars.
To uncover these findings, the NANOGrav team, comprising scientists from the US and Canada, meticulously timed radio wave pulses from an array of 67-millisecond pulsars in our galaxy over 15 years. They used the world’s largest telescopes, including the Arecibo Observatory in Puerto Rico, the Green Bank Telescope in West Virginia, and the Very Large Array in New Mexico.
Discerning the Gravitational Wave Background
Three years after initially spotting a signal, a consistent “hum” across all pulsars, the NANOGrav team now has compelling evidence for the gravitational wave background’s existence. The next phase involves using these observations to study the sources of this cosmic hum.
The most likely contributors to the gravitational wave background are pairs of supermassive black holes locked in a death spiral. NANOGrav’s discovery of the gravitational wave background may provide the answer to the long-standing “final parsec problem,” suggesting that black holes indeed merge after drawing close enough.
A Universe Resonating with Supermassive Black Hole Duets
By examining the intensity of the gravitational wave background, scientists estimate that hundreds of thousands or potentially over a million supermassive black hole pairs populate the universe. But not all detected gravitational waves must be from these black hole pairs.
Predictions from string theory or alternative theories about the universe’s birth suggest other possible sources of ultra-low-frequency gravitational waves. However, an unknown variability in pulsars may also be skewing NANOGrav’s results.
Charting the Cosmic Symphony’s Future
The NANOGrav team plans to delve deeper into potential contributors to the detected gravitational wave background and continue monitoring the pulsars. They hope to decipher the background based on the waves’ frequency and origin.
Other global collaborations also report hints of the gravitational wave background. These groups pool data through the International Pulsar Timing Array consortium to better understand the signal and its sources. This combined data promises to unlock deeper secrets of our universe.
Meta Description: Unveiling the symphony of gravitational waves, NANOGrav scientists have opened a new chapter in observing the cosmos. Their 15-year study of pulsars reveals new insights about supermassive black holes and potential string theory predictions.
