In this artist’s interpretation, a pair of supermassive black holes (top left) emits gravitational … [+] waves that ripple through the fabric of space-time. Those gravitational waves compress and stretch the paths of radio waves emitted by pulsars (white). By carefully measuring the radio waves, a team of scientists recently made the first detection of the universe’s gravitational wave background.
A team of international scientists have found the first evidence of a cosmic gravitational wave background across the universe. They think it could be produced by hundreds of thousands of pairs of supermassive black holes orbiting each other for a couple million years before they merge.
The stunning new discovery of these rumbles or ripples in space-time in the background of the universe were made by detecting their distorting effect on light coming from pulsars, rapidly spinning dead stars that pulse every millisecond.
Although short wavelength gravitational waves were first discovered in 2015 from the merger of small black holes, this is the first time long wavelength gravitational waves have been discovered—as predicted by Albert Einstein in his theory of general relativity in 1916.
The new discovery could help astronomers locate specific supermassive black holes orbiting each other (called binaries), which have so far proved elusive despite being predicted.
Galaxy-Sized Detector
By using 68 pulsars across the Milky Way, the astronomers were able to construct a galaxy-sized gravitational-wave detector. The 15-year study found gravitational waves that are very low frequency, with wavelengths of a few light years.
“This is key evidence for gravitational waves at very low frequencies,” said Stephen Taylor at Vanderbilt University, who co-led the search and is the current chair of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration, one of the groups involved in a paper on the detection published yesterday in The Astrophysical Journal Letters. “After years of work, NANOGrav is opening an entirely new window on the gravitational-wave universe,” he added.
Ripples In Space-Time
What the scientists found was evidence that the precise rhythms of the light coming from the pulsars are affected by the periodic stretching and squeezing of space-time by these long-wavelength gravitational waves in the background.
This is not the first time that gravitational waves have been detected. That honor went to the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015, which found short-wavelength fluctuations in space-time caused by the merger of smaller black holes and some neutron stars.
The Lovell Telescope at the Jodrell Bank Observatory, Cheshire, United KIngdom was one of six radio … [+] telescopes used (Photo by Peter Byrne/PA Images via Getty Images)
This detection of long-wavelength gravitational waves propagating in space is on a vastly different scale and was made using six of the largest radio telescopes in Europe and India:
- 100-m radio telescope in Effelsberg (Germany)
- Westerbork Synthesis Radio Telescope (Netherlands)
- Lovell Telescope at Jodrell Bank Observatory (United Kingdom)
- Sardinia Radio Telescope (Italy)
- Nançay Radio Telescope (France)
- Giant Metrewave Radio Telescope (India)
Other explanations for what causes this gravitational wave background include cosmic inflation or cosmic strings. “We think binaries are much more likely,” said Luke Zoltan Kelley, assistant adjunct professor of astronomy at the University of California, Berkeley. “To really be able to definitively say that this is coming from binaries, however, what we have to do is measure how much the gravitational wave signal varies across the sky.”
Wishing you clear skies and wide eyes.
