Galaxies’ missing mass may hide in gas clouds

Huge amounts of cold matter surround star-containing regions, study finds

1:07pm, January 13, 2014

HIDDEN GAS  Galaxies like Messier 81, a spiral galaxy in the constellation Ursa Major, are surrounded by vast quantities of cold, nonluminous gas, a new study finds.

OXON HILL, Md. — Vast reservoirs of previously undetected gas account for much of galaxies’ mass, according to research presented January 7 at a meeting of the American Astronomical Society. The finding could explain why earlier studies found far less mass in galaxies than cosmologists’ theories had predicted.

For more than a decade, astronomers have wondered about galaxies’ missing mass. Baryonic matter — the ordinary, visible stuff of the universe including the protons, neutrons and electrons that make up stars and planets — should account for about 17 percent of a galaxy’s matter; the rest is invisible dark matter. But when researchers try to estimate the  amount of baryonic matter in stars and in the 1 million degree Celsius and hotter gas that surrounds galaxies in giant halos, astronomers can account for only around a third of the baryonic matter they think galaxies should have.

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