The Pinwheel Galaxy (also known as Messier 101, M101) is one of the largest disk galaxies known with a visible diameter of 170,000 light years. This grand-design face-on spiral galaxy is located at a distance of 27 million light-years from us in the constellation Ursa Major
A unique feature of M101 is the high population of extremely bright star-forming regions (called H II regions) scattered across its spiral arms. Observational evidence indicates that close gravitational interaction with companion galaxies created waves of high mass and condensed gas which continue to orbit the galaxy centre. These tidal forces compress interstellar hydrogen gas, which then triggers strong star formation activity. The lopsided asymmetric structure of M101 is also due to the tidal forces from these local gravitational interactions.
Right ascension: 14h 03m 11.88s | Declination: +54° 21′ 00″ | Distance: 27 Million Light Years | Field of view: 37.4 x 24.9 arcmin
Camera: SBIG STL-6303E
Telescope: PlaneWave Instruments CDK 12.5 F/7.9
Guiding: External 80mm F/4 guidescope with an Atik 314L+ for guiding
Mount: Paramount PME
Filters: Astrodon Series E LRGB
Exposures: Luminance (34 x 5min), Red (12 x 5min), Green (14 x 5min), Blue (13 x 5min)
Binning: Luminance 1×1, RGB 2×2
Total exposure: 6 hours
Image composition: LRGB
Scale: 0.73 arcsec/pixel
Image acquired: Over 8 nights during May & June 2013
Image capture with MaxIm DL, FocusMax, ACP; Image processed with MaxIm DL, PixInsight, Photoshop CS4