M101 - Pinwheel Galaxy
Messier 101 or M101 (also designated NGC 5457) is a spiral galaxy in the constellation Ursa Major. It has an apparent visual magnitude of 7.9 and its angular diameter is 22 arc-minutes. M101 lies at an estimated distance of 27 million light years. The Equinox 2000 coordinates are RA= 14h 03.2m, Dec= +54° 21´ which makes M101 best seen during the spring. The Messier Spring Star Chart shows the position of all Messier objects visible during that season. As one of the more famous objects in the Messier Catalog, it is commonly known as the Pinwheel Galaxy.
The image above shows the uncropped view of M101 through the Takahashi E-180 Astrograph.
This spiral galaxy was discovered by P. Méchain in 1781. The 3rd Earl of Rosse identified it as a "spiral nebulae" in 1851. The Pinwheel Galaxy is a face-on spiral which appears somewhat asymmetric. According to Stoyan et al. (2010), the distance of M101 is 21.8 million light years and its diameter is 184,000 light years. This makes it about twice the size of the Milky Way Galaxy. Its mass is on the order of 100 billion solar masses.
For more information, see the Messier Catalog as well as specific entries for M101 in Wikipedia and SEDS.
Messier's Description of M101
March 27, 1781
`Nebula without star, very obscure and pretty large, of 6 or 7 minutes
[of arc] in diameter, between the left hand of Bootes and the tail of
the great Bear [Ursa Major]. It is difficult to distinguish when one lights
the [graticule] wires.'
(diam. 7')
Technical Details
- Object: M101
- Other Names: NGC 5457, Pinwheel Galaxy
- Object Type: spiral galaxy
- Object Data: Apparent Magnitude = 7.9, Angular Size = 22 arc-minutes
- Object Position (Equinox 2000): RA= 14h 03.2m, Dec= +54° 21´, Constellation = Ursa Major
- Date/Time: 2022 Mar 06/07 UTC
- Location: Bifrost Astronomical Observatory, Portal, AZ
- Mount: Astro-Physics 1100GTO
- Telescope: TPO 12-inch f/4 Imaging Newtonian (FL = 1220mm)
- Guiding: SVBONY SV106 60mm Guide Scope + ZWO ASI120MM Mini Guide Camera
- Coma Corrector: Sky Watcher Quattro Coma Corrector
- Camera: ZWO ASI2600MC Pro
- Field of View: 62.5' x 41.6'; at 0.6 arc-sec/pixel
- Exposure: 32 x 300s, f/4
- Total Exposure: 2h 40m
- File Name: M101-TPO01.jpg
- Processing: Deep Sky Stacker, Pixinsight, Photoshop CC
- Original Image Size: 4176 × 6248 pixels (26 MP); 13.9" x 20.8" @ 300 dpi
- Rights: Copyright 2023 by Fred Espenak. All Rights Reserved. See: Image Licensing.