M 101 – NGC 5457


Click on the image to see a larger version


M 101 is a large, face-on spiral galaxy that was discovered by Mechain in 1781. It was added to Messier catalog that same year and it was one of its last entries. Despite its magnitude, +7.9, its surface brightness is low (its light is spread over 30×27 arcmin) and it is not easy to observe or capture. M 101 is a quite large galaxy, about twice the Milky Way’s diameter. M 101 is part of a group of several galaxies (it is the brightest member) and the gravitational encounters with other members of the group may have provided the current “asymmetrical” appearance that can be seen today. It has many HII regions, more than 3000 can be seen in pictures, meaning a high star-birthrate.

Additional Information


Name(s): M 101. NGC 5457. Pinwheel Galaxy.

Type: Spiral galaxy

RA:  14h 03m 11s

Dec: +59º 21’ 06”

Constellation: Ursa Major

Size (arcmin): 30×27

Magnitude: +7.9

Distance: 27 Mly


Date: 2014-04-23

Location: iTelescope.net, Mayhill, NM, USA

Size (arcmin): 49×33

Telescope: 17” f/4.5

Camera: SBIG STL 11000M (4008x2672pix)

Guiding: yes

Total exposure: 68 min (L. 24min; RGB 44 min)

Processing: CCDStack, Photoshop CC 2016 and PixInsight


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