Heart of darkness could explain sun mysteries

IS DARK matter lurking at the centre of our bright sun? Yes, say two research groups who believe the elusive stuff is cooling the solar core.

The insight doesn't significantly affect the sun's overall temperature. Rather, a core chilled by dark matter would help explain the way heat is distributed and transported within the sun, a process that is poorly understood.

Dark matter doesn't interact with light and so is invisible. The only evidence for its existence is its gravitational effects on other objects, including galaxies. These effects suggest dark matter makes up about 80 per cent of the total mass of the universe.

The idea that it might lurk at the heart of the sun goes back to the 1980s, when astronomers found that the number of ghostly subatomic neutrinos leaving the sun was only about a third of what computer simulations suggested it should be. Dark matter could have explained the low yield because it would absorb energy, reducing the rate of the fusion reactions that produce neutrinos.

However, the problem was solved another way when it was found that neutrinos oscillate between three kinds, only one of which was being detected on Earth. As a result, the idea of solar dark matter was dropped.

Now it is being resurrected in the light of recent searches for dark matter, which have put limits on the mass of the particles that it is made of and shown that it interacts only very weakly with ordinary matter. These led Stephen West of Royal Holloway, University of London, and his colleagues to explore what would happen if particles that fell within these limits exist in the sun.

Their simulations show that gravity would pull such dark particles to the centre of the sun, where they would absorb heat. Some of these dark matter particles would then carry this heat from the core to the surface, decreasing the core temperature


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