NS: Missing matter has no place to hide

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NS: Missing matter has no place to hide

Post by bystander » Tue Mar 23, 2010 7:06 pm

Missing matter has no place to hide
New Scientist - 2010 March 23
Missing: more than half of the Milky Way.

Galaxies contain much less ordinary matter, in the form of stars and gas, than observations of the afterglow of the big bang suggest. One theory is that this missing matter hides in a halo of hot gas around each galaxy.

Now Michael Anderson and Joel Bregman of the University of Michigan in Ann Arbor have used light from pulsars beyond the Milky Way to probe the halo.

Gas slows down some wavelengths of light more than others, but the pair found only small delays in the pulsar light, implying there is less gas in the halo than needed to explain the missing matter.

Stellar explosions may have prevented some matter from joining early galaxies, they say.
Do Hot Haloes Around Galaxies Contain the Missing Baryons?