Explanation: Just like our own Milky Way Galaxy, the nearest major galaxy M31 has many star systems spewing high energy radiation. High energy X-radiation is visible to certain satellites in Earth orbit such as ROSAT - which took the above picture. The X-ray sources in M31 occur in globular clusters, the spiral arms, and near the galaxy's center. Probably most of these sources are accretion disk binary star systems. M31 has more X-ray sources near its center than our Galaxy, and the reason for this is currently unknown.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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