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Astrophysicists using large radio telescopes to observe a collection of cosmic clocks in our Galaxy have found evidence for gravitational waves that oscillate with periods of years to decades, according to a set of papers published today in The Astrophysical Journal Letters. The gravitational-wave signal was observed in 15 years of data acquired by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Physics Frontiers Center (PFC), a collaboration of more than 190 scientists from the US and Canada who use pulsars to search for gravitational waves. International collaborations using telescopes in Europe, India, Australia and China have independently reported similar results.
While earlier results from NANOGrav uncovered an enigmatic timing signal common to all the pulsars they observed, it was too faint to reveal its origin. The 15-year data release demonstrates that the signal is consistent with slowly undulating gravitational waves passing through our Galaxy.
“This is key evidence for gravitational waves at very low frequencies,” says Vanderbilt University’s Dr. Stephen Taylor, who co-led the search and is the current Chair of the collaboration. “After years of work, NANOGrav is opening an entirely new window on the gravitational-wave universe."
Unlike the fleeting high-frequency gravitational waves seen by ground-based instruments like LIGO (the Laser Interferometer Gravitational-wave Observatory), this continuous low-frequency signal could be perceived only with a detector much larger than the Earth. To meet this need, astronomers turned our sector of the Milky Way Galaxy into a huge gravitational-wave antenna by making use of exotic stars called pulsars. NANOGrav’s 15-year effort collected data from 68 pulsars to form a type of detector called a pulsar timing array.
A pulsar is the ultra-dense remnant of a massive star's core following its demise in a supernova explosion. Pulsars spin rapidly, sweeping beams of radio waves through space so that they appear to “pulse” when seen from the Earth. The fastest of these objects, called millisecond pulsars, spin hundreds of times each second. Their pulses are very stable, making them useful as precise cosmic timepieces.
While earlier results from NANOGrav uncovered an enigmatic timing signal common to all the pulsars they observed, it was too faint to reveal its origin. The 15-year data release demonstrates that the signal is consistent with slowly undulating gravitational waves passing through our Galaxy.
“This is key evidence for gravitational waves at very low frequencies,” says Vanderbilt University’s Dr. Stephen Taylor, who co-led the search and is the current Chair of the collaboration. “After years of work, NANOGrav is opening an entirely new window on the gravitational-wave universe."
Unlike the fleeting high-frequency gravitational waves seen by ground-based instruments like LIGO (the Laser Interferometer Gravitational-wave Observatory), this continuous low-frequency signal could be perceived only with a detector much larger than the Earth. To meet this need, astronomers turned our sector of the Milky Way Galaxy into a huge gravitational-wave antenna by making use of exotic stars called pulsars. NANOGrav’s 15-year effort collected data from 68 pulsars to form a type of detector called a pulsar timing array.
A pulsar is the ultra-dense remnant of a massive star's core following its demise in a supernova explosion. Pulsars spin rapidly, sweeping beams of radio waves through space so that they appear to “pulse” when seen from the Earth. The fastest of these objects, called millisecond pulsars, spin hundreds of times each second. Their pulses are very stable, making them useful as precise cosmic timepieces.
