WHERE are all the missing galaxies that should be orbiting the Milky Way? Cosmic rays may have 鈥渟terilised鈥� them so that they cannot form new stars and so are now too dim to see.
Standard theories of dark matter and galactic evolution predict that a few thousand dwarf galaxies should be spiralling around our galaxy, but a mere 35 have been found. Many are very faint, though, suggesting others might not be missing but instead are unseen blobs of dark matter.
Now, and of the Max Planck Institute for Astrophysics in Garching, Germany, say cosmic rays from sparse supernovae inside these small galaxies pelt the surrounding gas, which then has trouble collapsing into stars due to the rays鈥� high energies. Their computer simulations of galaxy formation are the most detailed yet ().
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