Hundreds of Invisible "X" Galaxies Predicted Orbiting the Milky Way

The outer edges of the Milky Way's appear to be orbited by innumerable invisible galaxies, one of which appears to be crashing into our own. Back in 2005 astronomers discovered the first evidence of mysterious dark galaxies with no starlight - VIRGOHI 21 - a mysterious cloud of hydrogen in the Virgo Cluster 50 million light-years from the Earth found to be colliding with our galaxy - revealed its existence from radio waves from neutral hydrogen coming from a rotating cloud containing enough hydrogen gas to spawn 100 million stars like the sun and fill a small galaxy.

The rotation of VIRGOHI21 is far too fast to be consistent with the gravity of the detected hydrogen. Rather, it implies the presence of a dark matter halo with tens of billions of solar masses. Given the very small number of stars detected, this implies a mass-to-light ratio of about 500, far greater than that of a normal galaxy (which would be around 50). The large gravity of the dark matter halo in this interpretation explains the perturbed nature of the nearby spiral galaxy NGC 4254 and the bridge of neutral hydrogen extending between the two entities.

VIRGOHI21 proved to be the first discovery of the dark galaxies anticipated by simulations of dark-matter theories. Although other dark-galaxy candidates have previously been observed, follow-up observations indicated that these were either very faint ordinary galaxies or tidal tails.

A dark galaxy is an area in the universe containing a large amount of mass that rotates like a galaxy, but contains no stars, held together by dark matter. Without any stars to give light, it could only be found using radio telescopes. It was first seen with the University of Manchester's Lovell Telescope in Cheshire, and the sighting was confirmed with the Arecibo telescope in Puerto Rico.

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Wow.

energon. it all is amazing. :)

Why no accretion?

Wont this change the current dark matter calculations by a huge factor?

I don't think it will really affect the predicted amounts of dark matter--it just seems that some it's been located.

"Dead" galaxies would be mostly helium. Wierd that no stars formed. This goes to show that what we really know about the universe just barely scratches the surface.