ars technica | Science | 09 Sept 2010
How can we use neutrinos to probe dark matter in the Sun?The evidence for dark matter has come from big objects, generally starting at galaxy-sized and going up from there to the structure of the Universe itself. But a paper in today's issue of Science indicates that we can look to something smaller (and much closer) if we want to start figuring out what dark matter looks like: our own Sun. Since dark matter interacts primarily through gravity, the Sun should have the largest concentration around, and the paper argues that the additional matter should influence the production of neutrinos in a way that we may be able to detect.
The paper is a Brevia, and its text doesn't even take up a full page, but it packs a lot of information into that short space. Its authors point out that the sun will gravitationally capture dark matter as it moves through the Milky Way and, provided these particles can at least undergo rare and weak collisions with regular matter, they'll eventually accumulate in the Sun's core. Once there, they'll influence the fusion reactions that take place.
According to our current model of the Sun, different reactions take place at different depths, and this should lead to an uneven distribution of the neutrinos these reactions produce. The dark matter will shift these reaction locations, and cause detectable differences in the neutrino flux coming out of the Sun. Right now, we don't have the hardware to detect these differences, but the authors say they should be within reach of future neutrino observatories.
It's worth noting that the dark matter-solar model they use contains a few assumptions beyond weak interactions with regular matter, such as the mass of the particles themselves and their ability to annihilate each other upon collisions. But the authors show how changing these assumptions can produce significantly different results. This means that, even if future experiments don't provide convincing evidence of dark matter, they could at least rule out several potential models of what the dark matter particles themselves look like.
PhysOrg | Astronomy | 09 Sept 2010
The existence of Dark Matter particles in the Sun's interior seems inevitable, despite dark matter never having been observed (there or elsewhere), despite intensive ongoing searches. Once gravitationally captured by the Sun, these particles tend to accumulate in its core.
In a paper to be published in the scientific journal Science, Dr. Ilidio Lopes and Professor Joseph Silk propose that the presence of dark matter in the Sun's interior causes a significant drop in its central temperature. Their calculations have shown that, in some dark matter scenarios, an isothermal solar core (constant temperature) is formed. The authors suggest that the neutrino detectors will be able to measure these types of effects.
In another paper published in The Astrophysical Journal Letters, the same authors suggest that, through the detection of gravity waves produced in the Sun's interior (identical to internal sea waves), Helioseismology can also independently confirm the presence of Dark Matter in the Sun.
Current detectors of solar neutrinos, Borexino and "Sudbury Neutrino Observatory" (SNO), as well as those currently being built, will be able to measure with precision the temperature in the Sun's interior. In particular, SNO is a Canadian experiment which also has European and American support. Portugal participates in the SNO and SNO+ experiments through the "Laboratório de Instrumentação e Partículas (LIP)".
The development of Helioseismology has been fundamental for increasing our scientific understanding of the Sun. The experiment Global Oscillation Low-degree Modes (GOLF) detector on the SoHO satellite seems to have identified gravity waves in the Sun for the first time. Future experiments in Helioseismology will be able to confirm these results.