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Pinwheel Galaxy

M101, NGC 5457

Proper NamePinwheel Galaxy
Messier NumberM101
NGC/IC NumberNGC 5457
ConstellationUrsa Major
Right Ascension14h 3m 13s
Declination+54° 20' 56"
Distancec.23,200,000 light years
c.7,100,000 parsecs
MagnitudeApparent: +7.77
Absolute: -21.49
DiameterApparent: 24.0' x 23.1'
Actual: 161,800 light years
Hubble TypeSABc intermediate spiral
Optimum VisibilityMay (Usually visible from northern latitudes)

Imagery provided by Aladin sky atlas

A galaxy of intermediate spiral form with its plane angled so that its spiral shape is clearly visible to an observer on Earth, some twenty-three million light years away. The Pinwheel is not 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 extensive 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 to the west of that constellation's border with Boötes. It lies close to the 'handle' of the Plough or Big Dipper, forming the third point of a roughly equilateral 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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