Dark Matter, now we see evidence in local space.

Currently, the most solid evidence of dark matter comes from  analyzing the Cosmic Microwave Background, and from the observed flatness of the galactic rotation curves. It is less known than in our galaxy the support for dark matter comes from studying the rotation curves at distances of 20 kpc or more from the galactic center. In the immediate neighborhood of the Sun (8 kpc from ground zero), the presence of dark matter is more difficult to deduce.

The recent paper by Moni Bidinattempted to measure the local Dark Matter density by observing gravitational effects on stellar motion near the Sun. The basic idea was to look at the orbits of stars above the galactic plane; if there is a Dark Matter halo around our galaxy, the matter inferred from gravitational effects on the orbits of visible stars will continue to grow, even as we look at stars farther above the galactic plane. The Moni Bidin paper found that stellar orbits implied only effects from the visible matter in the galactic plane. However…


A new paper by Bovy and Tremaine examine an assumption of the Moni Bidin paper and find it is in error. Correcting for this error restores consistency between the observed data and the Dark Matter halo hypothesis. The idea behind the Moni Bidin paper is sound, and in fact provides as far as I know the first observational evidence for local Dark Matter. In any case, we should soon have new results by examining other surveys of stellar motion.

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