The Pinwheel Galaxy
 |
| Observation data (J2000 epoch) |
The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy distanced 21 million light-years (six megaparsecs)away in the constellation Ursa Major, first discovered by Pierre Méchain on March 27, 1781, and communicated to Charles Messier who verified its position for inclusion in the Messier Catalogue as one of its final entries.
On February 28, 2006, NASA and the ESA released a very detailed image of the Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the time. The image was composed from 51 individual exposures, plus some extra ground-based photos.
 |
| This image of M101 combines data in the infrared, visible, ultraviolet and x-rays from four of NASAs space telescopes. This multi-spectral view shows that both young and old stars are evenly distributed along M101s tightly-wound spiral arms. |
On August 24, 2011, a Type Ia supernova, SN 2011fe, was discovered in M101.
Pierre Méchain, the discoverer of Messier 101, described it as a "nebula without star, very obscure and pretty large, 6' to 7' in diameter, between the left hand of Bootes and the tail of the great Bear. It is difficult to distinguish when one lits the [grating] wires."
William Herschel noted in 1784 that "[M101] in my 7, 10, and 20-feet [focal length] reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will, perhaps, render the stars visible of which I suppose them to be composed."
Lord Rosse observed M101 in his 72-inch [diameter] Newtonian reflector during the second half of the 19th century. He was the first to make extensive note of the spiral structure and made several sketches.
To observe the spiral structure in modern instruments requires a fairly large instrument, very dark skies, and a low power eye piece.