M17- 5.21.2006
Image Capture Details

Optics:  Orion ED80mm
Mount: Meade LX200
Camera: Canon Digital Rebel 350XT
Filters: Sirius V-Block

Focal Ratio:  F/7.5

Guiding with Meade DSI

Exposure:
26 X 120 Seconds for image depth.
Layered Mask and cropped  in
Photoshop
Time: 2:26am - 3.24am EST
Location: Waldwick, NJ
Click here to see the
original un-cropped
wide angle image.
The Omega Nebula M17, also called the Swan Nebula, the Horseshoe Nebula, or (especially on 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. 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 obscurred stars seems to be imbedded in the nebulosity.

The color of the Omega Nebula is reddish, with some graduation to pink. This color comes from the hot hydrogene 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 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. 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.  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, thus little less than that of its apparent neighbor, M16 with the Eagle nebula -
apparently, these two star forming regions are indeed close together, in the same spiral arm (the Sagittarius or Sagittarius-Carina arm) of the Milky
Way galaxy, and perhaps part of the same giant complex of cosmic clouds of interstellar matter.


1 http://www.seds.org/messier/m/m017.html
© 2007 David A. Trapani
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