Scientists Uncover New Data on the Nature of Dark Matter

Recent research may reveal a bit more about the nature of dark matter. Scientists have set limits to the properties of one of the particles which aspire to be identified as dark matter: axions.

Dark matter amounts to more than 80 percent of the universe, according to the indirect evidence of its gravitational effects. So far, though, scientists have been unable to directly detect dark matter. That's why researchers have been studying particles to see which are good candidates.

In this latest study, the scientists used stars as particle physics labs. With the high temperature inside stars, photons turn into axions that escape to the exterior, carrying energy with them.

"This loss of energy can have consequences, whether they are observable or not, in some phases of stellar evolution," said Adrian Ayala, one of the researchers, in a news release. "In our research, we have conducted numerical simulations (by computer) of the evolution of a star, since its birth until it exhausts all of the hydrogen first and then the helium in its interior, including the processes that produce axions."

The researchers found that the emission of axions can significantly diminish the time for the central combustion of helium, the so called HB (Horizontal Branch) phase. The energy taken by axions is compensated with the energy provided by nuclear combustion, which leads to a much faster consumption of helium.

"Using this influence over the timing that features in this sort of evolution we can determine the emission of axions, since a high emission rate means a quick HB phase, thus diminishing the possibility of watching stars in this phase," said Immaculada Dominguez, one of the researchers.

The researchers used the high quality observations to examine the contrast between results of the numerical observations and actual data. They compared the amount of stars observed in the HB phase with the amount of stars in a different phase not affected by axions to estimate the maximum axion emission rate.

The findings reveal a bit more about axions. This, in turn, could help scientists learn a bit more about the nature of dark matter in the future.

The findings are published in the journal Physical Review Letters.

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