Scientists might have heard the background ‘hum’ of the universe for the first time

Scientists have captured what might be the background ‘hum’ of the universe, a resonating echo created by incredibly violent collisions in the universe’s past.

The ‘hum’ isn’t sound, of course (as there’s no air in space) - instead, it’s thought to be gravitational waves, created by impacts between objects such as black holes.

Scientists at the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) predicted that the hum (or ‘gravitational wave background’) would be detectable, according to ScienceAlert.

The researchers believe it could hold important clues to our universe’s history - and could help us understand objects such as black holes.

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Joseph Simon, of Nanograv, said, "It is incredibly exciting to see such a strong signal emerge from the data.”

"However, because the gravitational-wave signal we are searching for spans the entire duration of our observations, we need to carefully understand our noise.

“This leaves us in a very interesting place, where we can strongly rule out some known noise sources, but we cannot yet say whether the signal is indeed from gravitational waves.”

NANOGrav researchers studied the signals from distant pulsars – small, dense stars that rapidly rotate, emitting beamed radio waves, much like a lighthouse – have used radio telescopes to collect data that may indicate the effects of gravitational waves, as reported in The Astrophysical Journal Letters.

Gravitational waves are ripples in space-time caused by the movements of incredibly massive objects, such as black holes orbiting each other or neutron stars colliding.

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Astronomers cannot observe these waves with a telescope like they do stars and galaxies. Instead, they measure the effects passing gravitational waves have, namely tiny changes to the precise position of objects - including the position of the Earth itself.

NANOGrav chose to study the signals from pulsars because they serve as detectable, dependable galactic clocks. But gravitational waves can disrupt those signals.

By studying the timing of the regular signals from many pulsars scattered over the sky at the same time, known as a “pulsar timing array,” NANOGrav detects minute changes in the Earth’s position due to gravitational waves stretching and shrinking space-time.

“NANOGrav has been building to the first detection of low frequency gravitational waves for over a decade and today’s announcement shows that they are on track to achieving this goal,” said Pedro Marronetti, NSF programme director for gravitational physics.

“The insights that we will gain on cosmology and galaxy formation are truly unparalleled.”

NANOGrav is developing techniques to ensure the detected signal could not be from another source.

Scott Ransom, from the National Radio Astronomy Observatory, and the current chair of NANOGrav says, “Trying to detect gravitational waves with a pulsar timing array requires patience. We’re currently analyzing over a dozen years of data, but a definitive detection will likely take a couple more.

“It’s great that these new results are exactly what we would expect to see as we creep closer to a detection.”

Like light from distant objects, gravitational waves are a cosmic messenger signal – one that holds great potential for understanding “dark” objects, like black holes.

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