Dark Matter May Be Building Up Inside the Sun
The sun could be a net for dark matter, a new study suggests. If dark matter happens to take a certain specific form, it could build up in our nearest star and alter how heat moves inside it in a way that would be observable from Earth.
Because lightweight dark matter particles wouldn’t vaporize each other when they meet, the sun should collect the particles the way snowballs collect more snow. The sun has been whizzing around the galaxy for 5 billion years, sweeping up all the dark matter as it goes.
The buildup of dark matter could solve a pressing problem in solar physics, called the solar composition problem. Sensitive observations of waves on the sun’s surface have revealed that the sun has a much easier time transporting heat from its interior to its surface than standard models predict it should.
Dark matter particles that interact only with each other could make up the difference. Photons and particles of regular matter bounce off each other on their way from the sun’s interior to its surface, so light and heat can take billions of years to escape. But because dark matter particles ignore all the regular matter inside the sun, they have less stuff in their way and can transport heat more efficiently.
Scientists calculated how being full of dark matter would affect the number of neutrinos the sun gives off. They found that the neutrino flux would change by a few percent, enough to be detected by two different neutrino experiments — one in Italy called Borexino and one in Canada called SNO+ — that are soon to get under way.
Some puzzling results from dark matter detectors hint that these lightweight particles could have already been detected. Earlier this year, a germanium hockey puck in a mine in Minnesota called the Coherent Germanium Neutrino Technology (CoGeNT) detected a signal from a particle about 7 times the mass of the proton, though they’re not sure yet whether it’s dark matter. Another detector in Italy called DAMA has reported similar results.
There’s an increasingly compelling body of evidence accumulating that dark matter is just a few times as massive as a proton. The jury is still out, but if this is really what’s going on, we should be able to know it with some confidence in the next year or so.