Missing Dark Matter

Dark matter is one of the greatest cosmic mysteries of our time, an invisible, intangible material thought to make up five-sixths of all matter in the universe.

Scientists currently think it is composed of a new type of particle, one that interacts normally with gravity but only very weakly with all the other known forces of the universe. As such, dark matter is detectable only via the gravitational pull it generates. Astronomers first proposed the existence of dark matter to explain why stars moved the way they did in the Milky Way. It was as if extra matter was present, exerting a gravitational pull that influenced the motions of the stars. According to widely accepted theories, the neighborhood around the sun should be filled with dark matter, with billions of these particles rushing through us every second. However, the most accurate study yet of motions of stars in the Milky Way now has found no evidence for dark matter in a large volume around the sun. As said study lead author Christian Moni Bidin, an astronomer at the University of Concepción in Chile their results contradict the currently accepted models, the mystery of dark matter has just become even more mysterious. The scientists used telescopes at the La Silla Observatory and the Las Campanas Observatory, both in Chile, to map the motions of more than 400 red giant stars up to 13,000 light-years from the sun. This helped calculate the mass of material in the vicinity of the sun, in a volume four times larger than ever considered before. Dark matter models had predicted there should be about 0.9 to 2.2 pounds (0.4 to 1 kilograms) of dark matter in a volume the size of the Earth in the sun’s part of the galaxy. However, these new findings suggest there is at most 0.15 pounds (70 grams) of dark matter in that volume in our part of the Milky Way galaxy. According to Moni Bidin despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for, so if dark matter is not present where we expected it, a new solution for the missing mass problem must be found.
source:www.space.com