More than half of the expected number of baryons - subatomic particles that make up our everyday world, such as protons and neutrons - in the Milky Way are unaccounted for, but Anjali Gupta of Ohio State University in Columbus and her colleagues seem to have spotted the missing matter. They analysed X-ray satellite data and found evidence of a hot gas halo around the Galaxy extending for 100 kiloparsecs. The authors estimate the mass of the halo to be between 10 billion and 60 billion times the mass of the Sun. The cloud could account for the missing particles, they conclude.
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