TELESCOPE = 17.5 inch f4.5
OBSERVER = Rusty Fletcher 
LOCATION = Seguin Outdoor Learning Center 
DATE (Yr-Mo-Dy) = 2004-04-01
TIME (UT) = 08:38:17

Diffuse Nebula M17 (NGC 6618) in Sagittarius 

The Omega, Swan, Horseshoe, or Lobster Nebula 

The Omega Nebula M17, also called the Swan Nebula, the Horseshoe Nebula, or (especially in the southern hemisphere) the Lobster Nebula, is a region of star formation and shines by excited emission, caused by the higher energy radiation of young stars. Star formation is either still active in this nebula, or ceased very recently. A small cluster of about 35 bright but obscurred stars seem to be imbedded in the nebulosity. 

The color of the Omega nebula is reddish, with some graduation to pink, and the brightest region is actually of white color, 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. The mass of the gas has been estimated to amount about 800 times that of the Sun, enough for forming a conspicuous cluster, and a good deal more than that of the Orion nebula M42. 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. 

Right ascension 18 : 18.0 (hours : minutes)
Declination -16 : 12 (degrees : minutes)
Distance 5,500 light years
Visual magnitude 7.5

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