Scientists Detect Gravitational Wave Chorus Reverberating Across the Universe

In a groundbreaking discovery, scientists have successfully observed the subtle undulations caused by the movement of black holes, which gently stretch and compress the fabric of the universe.

The research team announced on Wednesday that they have “heard” the low-frequency gravitational waves, which represent alterations in the cosmic fabric generated by the immense celestial bodies traversing and colliding in space.

“This is the first instance where we have concrete evidence of the vast-scale motion encompassing the entirety of the universe,” stated Maura McLaughlin, co-director of NANOGrav, the research collective responsible for publishing these findings in The Astrophysical Journal Letters.

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Albert Einstein had predicted that when exceedingly massive entities move through the spacetime continuum—the very fabric of our universe—they produce ripples that propagate throughout this medium. These ripples have often been likened to the universal background melody.

In 2015, scientists deployed the LIGO experiment to successfully detect gravitational waves for the first time, thus validating Einstein’s theory. However, until now, these methods were only capable of capturing waves at higher frequencies, according to Chiara Mingarelli, an astrophysicist at Yale University and a member of NANOGrav.

Mingarelli clarified that these swift “chirps” occur when relatively small black holes collide with dead stars.

In their recent research, the scientists sought out waves with significantly lower frequencies. These gradual ripples take years or even decades to complete a full cycle and likely emanate from some of the largest objects in our universe: supermassive black holes, billions of times more massive than our sun.

As galaxies throughout the universe perpetually collide and merge, scientists theorize that the colossal black holes at their cores also draw closer to one another, engaging in an intricate cosmic dance before ultimately collapsing into a singular entity. These paired black holes emit gravitational waves as they orbit one another, forming binary systems.

“Serenely orbiting supermassive black hole binaries function as the tenors and bass of the cosmic symphony,” remarked Szabolcs Marka, an astrophysicist at Columbia University unaffiliated with the study.

Capturing the ripples emanating from these colossal objects proved impossible with conventional instruments on Earth. Consequently, Michael Lam from the SETI Institute, a researcher associated with NANOGrav, explained, “We needed to construct a detector of a scale roughly equivalent to that of the galaxy itself.”

The results disclosed this week incorporated 15 years’ worth of data collected by NANOGrav, which employed telescopes across North America to search for these waves. Several other teams of gravitational wave researchers from around the world also published studies, including groups from Europe, India, China, and Australia.

The scientists directed their telescopes toward pulsars, deceased stars emitting radio wave pulses akin to the flashes of a lighthouse as they rotate in space.

These pulses are incredibly regular, enabling scientists to anticipate the precise moment radio waves should reach our planet—akin to an impeccably accurate clock situated deep in space, elucidated Sarah Vigeland, a NANOGrav member and astrophysicist at the University of Wisconsin-Milwaukee. However, gravitational waves warp the fabric of spacetime, causing a fluctuation in the distance between Earth and the pulsars, disrupting their steady rhythm.

By meticulously analyzing minuscule fluctuations in the pulsars’ timing—some pulses arriving slightly earlier, while others lag behind—scientists could discern the presence of gravitational waves.

The NANOGrav team scrutinized 68 pulsars scattered across 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 research groups discovered similar evidence using telescopes situated across the globe.

To date, this methodology has not been able to pinpoint the exact origin of these low-frequency waves, remarked Marc Kamionkowski, an astrophysicist at Johns Hopkins University uninvolved in the research.

Rather, it has unveiled a perpetual hum that envelops us, analogous to standing amidst a bustling party, where countless conversations meld together, resulting in a general cacophony, Kamionkowski elucidated.

Mingarelli expressed surprise at the “louder” background noise discovered, suggesting that there might be more frequent or larger black hole mergers occurring in space than previously presumed. Additionally, these findings may indicate the existence of alternative sources of gravitational waves that challenge our current comprehension of the universe.

Researchers aspire to employ continued analysis of these gravitational waves to deepen our understanding of the most massive objects in our universe. This pursuit may unlock new avenues for “cosmic archaeology,” allowing us to trace the history of black hole and galaxy mergers transpiring all around us, as posited by Marka.

“We are beginning to open a new window into the universe,” Vigeland concluded.

The Big Big News Health and Science Department is supported by the Science and Educational Media Group of the Howard Hughes Medical Institute. The AP holds sole responsibility for all content.

Frequently Asked Questions (FAQs) about gravitational waves

More about gravitational waves

• The Astrophysical Journal Letters
• LIGO – Laser Interferometer Gravitational-Wave Observatory
• NANOGrav – North American Nanohertz Observatory for Gravitational Waves
• Albert Einstein and Gravitational Waves