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ngc 7662

 

Glowing brightly at about 9th magnitude, NGC 7662 is an archetypal multiple-shell planetary nebula. The nebula consists of several ellipsoidal shells of ionized gas, which emit visible light at discrete wavelengths. The most prominent of these emissions is from the flourescence of doubly-ionized Oxygen (OIII), which happens to emit a distinctive blue-green form of light. Early observers were able to visually detect this unique coloration in NGC 7662, an so gave it the common name "Blue Snowball"! The bright inner ring actually represents the edge of a hollow shell that has been partially evacuated by fierce winds from the nebula's hot central star. As this wind-driven shell of material expands, it literally plows into the denser outer shell of matter which was released hundreds of years earlier. Several other such regions can also be spotted along the outer edge of the more circular outer shell, which forms the main body of the nebula. All of these brightened areas represent portions of the nebula where faster moving material has caught up with slower moving matter, resulting in a "snowplow" effect. Also of note is the presence of a pair of tiny red objects known as FLIER's located just outside the main body of the nebula at about 2 o'clock and 8 o'clock from the central star. These Fast-moving Low Ionization Emission Regions remain a mystery to even those who study them! However, it seems that they are the equivalent to supersonic "bullets" of processed matter that were somehow ejected from the dense core of the nebula's central star. Image taken with homemade 12.5-inch f/6.9 astrograph and SBIG STL-11000M. LRGB image composed of 20 minutes of luminance and 10 minutes of red, combined with 30 minutes each R,G,B. Be sure to click on the above image for the high resolution version.