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M101, also called the "pinwheel galaxy", is a spiral galaxy in the constellation of the Ursa Major.
It is a Sc-type galaxy (non-compact spiral) seen exactly "in the face": its spiral arms are however very weak and visually visible only with large telescopes, while they are easy enough to reveal with long-exposure photographs.
Its distance from the Earth is about 24 million years ago, and its diameter is about 170,000 light years, so it is a galaxy that is considerably larger than our Milky Way.