M17 - Swan Nebula



About this image.

Discovered by Philippe Loys de Chéseaux in 1745-46.

The Omega Nebula M17, also called the Swan Nebula, or (especially on the southern hemisphere) the Lobster Nebula, is a region of star formation that shines by excited emission, caused by the higher energy radiation of young stars. Unlike in many other emission nebulae, however, these stars are not obvious in optical images, but hidden in the nebula. Star formation is either still active in this nebula, or ceased very recently. A small cluster of about 35 bright but obscured stars seems to be imbedded in the nebulosity.

The colour of the Omega Nebula is reddish, with some graduation to pink. This colour comes from the hot hydrogen gas which is excited to shine by the hottest stars which have just formed within the nebula. However, the brightest region is actually of white colour, not overexposed as one might think. This phenomenon is apparently a result of a mixture of emission light from the hottest gas, together with reflections of the bright star light from the dust in this region. The nebula contains a large amount of dark obscuring material, which is obvious in its remarkable features. This matter has been heated by the hidden young stars, and shines brightly in infrared light.

The mass of the gas has been estimated to amount about 800 times that of the Sun, enough for forming a conspicuous cluster. While the bright nebula seems to be roughly 15 light years in extension, the total gaseous cloud, including low-luminosity material, seems to extend to at least 40 light years. Distance estimates are spread over a wide range, but modern values are between 5,000 and 6,000 light years.

The discovery of M17 by De Chéseaux didn't get widely known, so Charles Messier independently rediscovered it and catalogued it on June 3, 1764.

(Text taken from www.seds.org)
 

Equipment

Telescope:                 12.5" Ritchey Chretien by RC Optical Systems
Mount:                      Paramount ME by Software Bisque
Instrument:               SBIG STL11K with AO-L
Exposure:                  HA:OIII:SII 1.5:5:6 hours
Capture Software:       CCDSOFT V5
Processing:                Maxim DL/CCD, Photoshop CS, CCDStack

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