LIGO team may have found dark matter

Not betting the house, but it's plausible, boffins say

Scientists think the recent discovery of gravitational waves observed from the collision of two black holes may have also detected signatures of the astrophysics mystery of dark matter.

Scientists at Johns Hopkins university behind the September 2015 discovery by Laser Interferometer Gravitational-Wave Observatory (LIGO) wrote in the Did LIGO detect dark matter? [pdf] the black hole pair, known as a binary, could be part of the hypothetical dark matter thought to make up 27 percent of non-dark energy mass and energy in the observable universe.

Their discovery came 100 years since Einstein's theory of General Relativity predicted the existence of gravitational waves.

Last week the LIGO team announced it had detected a second round of gravatitional waves, shoring up the certainty of the initial find.

The binary was sized at between 36 and 29 times the mass of our sun, which larger than most stellar black hole model predictions allow, but insufficient for supermassive black hole models.

It fits however with the model for the less-popular primordial black holes hypothesis in which the objects are said to be formed of collapsed gas during the early universe rather than dying stars.

These would distribute evenly throughout the universe and may congregate around galaxies.

The rate in which such primordial black holes would form binaries and collide matches with LIGO's observations, the scientists say.

"We are not proposing this is the dark matter," physics and astronomy professor Marc Kamionkowski says.

"We're not going to bet the house. It's a plausibility argument."

Further 30 solar-mass collisions would shore up the suggestion according to co-author and postdoctoral fellow Ely D. Kovetz.

"That the discovery of gravitational waves could be connected to dark matter" is creating lots of excitement.

Their suggestion could be put to the test earlier than otherwise expected. University of Glasgow physics professor Ken Strain told The Register this week that a gravitational wave event could be detected each month by the end of the decade thanks to LIGO upgrades in which he is involved.

Some US$600 million has already been spent upgrading LIGO to its advanced state.

"By the end of the decade we'll probably be able to detect at least one gravitational wave event per month," Ken Strain, professor of physics at University of Glasgow involved in upgrading LIGO, told The Register.

Two gravitational wave detectors are located in America and one in Italy with a further two to be constructed in India and Japan. ®


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