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Pinwheel Galaxy

M101, NGC 5457

A galaxy of spiral form with a plane angled so that its spiral shape is clearly visible to an observer on Earth, some 21 million light years away. The Pinwheel is not in fact a perfect spiral, but slightly asymmetrical in shape, a factor which is though the betray a collision or interaction with another galaxy at some point in the past. The Pinwheel is rather more expansive than the Milky Way, and has at least five smaller companion galaxies.

In the skies of Earth, the Pinwheel Galaxy falls within the constellation of Ursa Major, just within that constellation's border with Boötes. It lies close to the 'handle' of the Plough or Big Dipper, forming the third point of a rough triangle with the first two stars of the handle, Alkaid and Mizar. The galaxy itself is far too faint to detect with the naked eye, and a fairly powerful telescope is needed to resolve its distinctive spiral structure.


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