Supposedly the most convincing evidence for dark matter so far:
Scientists have observed dark matter, the elusive stuff that makes up a quarter of the universe, in isolation for the first time. By studying a galaxy cluster 3 billion light years away, Marusa Bradac of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), located at the Department of Energy’s Stanford Linear Accelerator Center (SLAC), and her colleagues made the landmark observations, which were announced today at a NASA teleconference. …
Dark matter is fundamentally different from luminous matter, which makes up only 4 percent of the mass of the universe. It is invisible to modern telescopes because it gives off no light or heat, and it appears to interact with other matter only gravitationally. In contrast, luminous matter makes up everything commonly associated with the universe—galaxies, stars, gases and planets.
Past observations have shown that luminous matter explains only a very small percentage of mass in the universe. The new research is the first to detect luminous matter and dark matter independent of one another, with the luminous matter clumped in one region and the dark matter clumped in another. These observations demonstrate the existence of two types of matter: one visible and one invisible.