Sun is Surrounded by Heaps of Dark Matter

 It was a Swiss astronomer Fritz Zwicky who first proposed the concept of Dark matter in the early 1930s.  He discovered how clusters of galaxies were filled with a mysterious dark matter that kept them from flying apart. At nearly the same time, Jan Oort in the Netherlands discovered that the density of matter near the Sun was nearly twice what could be explained by the presence of stars and gas alone. In the intervening decades, astronomers developed a theory of dark matter and structure formation that explains the properties of clusters and galaxies in the Universe, but the amount of dark matter in the solar neighborhood has remained more mysterious. 

 For decades after Oort's measurement, studies found 3-6 times more dark matter than expected. Then last year new data and a new method claimed far less than expected. But recently astronomers at the University of Zurich and the ETH Zürich, together with other international researchers, have found large amounts of invisible "dark matter" near the Sun.

 Their results are consistent with the theory that the Milky Way Galaxy is surrounded by a massive "halo" of dark matter, but this is the first study of its kind to use a method rigorously tested against mock data from high quality simulations.

The results are to be published in the journal Monthly Notices of the royal Astronomical Society and are available online.

In the latest work, the scientists said that they are confident in their measurements and its uncertainties, because state of the art simulation of our galaxy was used to test their technique for measuring the amount of material before applying it to real estate. This gave rise to a number of surprises

"We are 99 percent confident that there is dark matter near the Sun," said Dr Silvia Garbari, a lead author of the study accepted for publication in the Monthly Notices of the Royal Astronomical Society. "It could be the first evidence for a 'disc' of dark matter in our Galaxy, as recently predicted by theory and numerical simulations of galaxy formation. Or it could be that the dark matter halo of our Galaxy is squashed, boosting the local dark matter density," she said.

They found that standard techniques used over the past 20 years were biased, always tending to underestimate the amount of dark matter. They then devised a new unbiased technique that recovered the correct answer from the simulated data.

Prof. George Lake study co-author explains: "If dark matter is a fundamental particle, billions of these particles will have passed through your body by the time your finish reading this article. Experimental physicists hope to capture just a few of these particles each year in experiments like XENON and CDMS currently in operation. Knowing the local properties of dark matter is the key to revealing just what kind of particle it consists of."