The problem of dark matter came about when astronomers began to study galaxies, like our own Milky Way. If we look at the structure of the galaxy as it would appear from the outside, most of the Milky Way's 100 billion-plus stars lie in the galactic disk. Most of the stars are concentrated near the center of the disk around the nucleus and galactic bulge. Above and below the plane of the disk are a few hundred scattered globular clusters and a large, dim, round region called the halo.
Experiments can be divided into two classes: direct detection experiments, which search for the scattering of dark matter particles off atomic nuclei within a detector; and indirect detection, which look for the products of WIMP annihilations.
Experiments can be divided into two classes: direct detection experiments, which search for the scattering of dark matter particles off atomic nuclei within a detector; and indirect detection, which look for the products of WIMP annihilations.
NASA/Photo courtesy Ned Wright
Our home galaxy, the Milky Way
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