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The Object The Pinwheel Galaxy (also known as Messier 101 or NGC 5457) is a face-on spiral galaxy about 27 million light-years away in the constellation Ursa Major. It was discovered by Pierre Méchain on March 27, 1781, and he subsequently communicated his discovery to Charles Messier who verified its position and added it to the Messier Catalogue as one of the final entries. M101 is a relatively large galaxy compared to the Milky Way. With a diameter of 170,000 light-years it is nearly twice the size of the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small bulge of about 3 billion solar masses. Another remarkable property of this galaxy is its huge and extremely bright H II regions, of which a total of about 3000 can be seen on photographs. HII regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. HII regions are ionized by large numbers of extremely bright and hot young stars. On photographs M101 can be seen to be asymmetrical on one side. It is thought that in the recent past (speaking in galactic terms) M101 underwent a near collision with another galaxy and the associated gravitational tidal forces caused the asymmetry. In addition, this encounter also amplified the density waves in the spiral arms of M101. The amplification of these waves leads to the compression of the interstellar hydrogen gas, which then triggers strong star formation activity. Imager: James Edward Keeler Object: M101/NGC5457 Name: None Type: Galaxy. Constellation: Ursa Major Site: Mount Hamilton, California, USA Date: 1899 Telescope: Crossley 36" Reflector Optical System: Newtonian Reflector Mount: Other German Equatorial Mount Type: German Equatorial Camera: Not Known Camera Type: Not Known Details 8th June 1899; 4 hours exposure; Orientation South at Top; 36" Crossley Reflector, Lick Observatory, Mount Hamilton, California         Image: M101 is a magnificent bright face on spiral galaxy. It is not surprising that it was a popular target for pioneer astrophotographers. George Willis Ritchey had imaged M101 with the 60” Reflector at Mount Wilson in 1910. However it is an earlier image of M101 which is featured here, that taken by James Edward Keeler in 1899, just a year before his premature death in 1900. This undoubtedly is the finest early photograph of M101 taken. It is remarkable in that it was taken with a 36” Reflector, a much smaller instrument than Ritchey had used some ten years later. What is even more incredible is that the 36” Crossley Reflector used by Keeler was a ‘second hand’ cast off (but a very good one!), originally built by Andrew Ainslie Common in 1876; sold to Edward Crossley who then donated it to the Lick Observatory in 1893.         Imager: James Edward Keeler was a 19th Century American astronomer and a pioneer of spectroscopic astrophotography. He was born on the 10th September 1857 at La Salle, Illinois, United States. The family moved to Mayport, Florida in 1869, where the young Keeler first became interested in Astronomy. In 1875-77 he founded the Mayport Astronomical Society and used its meager equipment (a two inch achromatic refractor) to observe stars, planets and nebulae. He enrolled at John Hopkins University late in 1877 and graduated in 1881 after majoring in Physics and German. Shortly before receiving his degree he was appointed as an assistant astronomer at the Allegheny Observatory in Pittsburg. In 1885 was appointed to the staff of the new Lick Observatory at Mount Hamilton, California, and for a time he was the only astronomer there. Keeler was the first to observe the gap in Saturn's rings now known as the Encke’s Gap, using the 36-inch refractor at Lick Observatory on 7 January 1888. This feature had been named after Johann Encke, who had observed a much broader variation in the brightness of the A Ring. Keeler's work was acknowledged, when the second major gap in the A Ring, discovered by the Voyager probe, was named the Keeler Gap in his honour. He left Lick in May 1891 after being appointed director of the University of Pittsburgh's Allegheny Observatory in 1891. It was whilst at Allegheny that Keeler took up Photography as one of the means to make use of the meager resources the Observatory had, as opposed to the wealth of equipment available at Lick. In 1895, his spectroscopic study of the rings of Saturn revealed that different parts of the rings reflect light with different Doppler shifts, due to their different rates of orbit around Saturn. This was the first observational confirmation of the theory of James Clerk Maxwell that the rings are made up of countless small objects, each orbiting Saturn at its own rate. These observations were made with a spectrograph attached to the 13-inch Fitz-Clark refracting telescope at Allegheny Observatory. He returned to Lick Observatory as its director in 1898. In the brief time that was left to him, Keeler did not just concentrate on administrative matters he actively participated in research, and in particular using the 36” Crossley Reflector (built by Andre Ainslie Common in England) to capture some of the most magnificent images ever taken of Comets, Galaxies, Nebulae and Star Clusters. The objects photographed included, the Pleiades (M45), Trifid Nebula (M20), the Great Orion Nebula (M42), Brooks Comet of 1898, Hind’s Variable Nebula in Taurus (NGC 1555) and many of the brighter Herschel objects. In 1908 the results of Keeler’s work were posthumously published in “Photographs of Nebulae and Clusters Made with the Crossley Reflector, Publications of the Lick Observatory Volume VIII”. A number of the photographs included were taken after Keeler’s death. In 1899 he was awarded the Henry Draper medal for his work on Saturn’s rings. James Edward Keeler died shortly afterwards on the 12th August 1900 due to a stroke whilst recovering from a severe cold. He had married in 1891 and left a widow and two children. His ashes were interred in a crypt at the base of the 31-inch Keeler Memorial telescope at the Allegheny Observatory. In addition to the Keeler Gap in Saturn's rings, craters on Mars and the Moon are named in his honour, as is the asteroid 2261 Keeler.