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Milky Way
The galaxy that contains our Solar System, characterized by its barred spiral structure with multiple spiral arms extending from a central bar.
Source: esa.int
APODs including "Milky Way"
The X-ray Sources of M31
31/12/1995
Image Credit: NASA Astronomy Picture of the Day
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.