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Astr110 Photography Projects, Fall 2004

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NGC651,Chris Mills

Helix Nebula

NGC 651 is one part of the planetary nebula M76, along with NGC 650. It was discovered by Pierre Mechain on September 5, 1780. At first is was found to be without stars but Charles Messier found that it was composed of small stars. Also it was first erroneously detected to be a double nebula until in 1918 Heber D. Curtis correctly classified it as a single planetary nebula. According to Jeffery Bennett's The Cosmic Perspective, a planetary nebula is a glowing cloud of gas ejected from a low-mass star at the end of its life.

NGC 651, and M76 are commonly called the little dumbbell, or the butterfly nebula because of its distinct dumbbell, butterfly shape. The reason it has two numbers, NGC 651 and NGC 650, is because it was assigned them for each lobe, as stated earlier it once was thought to be two nebulas. The southern lobe, NGC 650, is brighter then the northern one, NGC 651. The thicker part of the nebula which is brighter and runs from the upper left to the lower right is called the 'bar' and the the two lobes on the left and the other on the right are usually called the 'wings'. The 'wings' of the nebula are formed by gas expanding significantly faster than that of the plane or 'bar' of the nebula.

References:

Bennett, Jeffery. The Cosmic Perspective. San Francisco Addison Wesley, 2002.

www.seds.org/messier/m/m076.html - 1999

http://www.siowl.com/Herschel400/html/ngc0651.htm

Right Ascension (J2000) 01.:42:18.00
Declination (J2000) +51:35:00.0
Filters used Clear
Exposure time per filter 300 seconds
Date/Time

November 17, 2004, 01:38:55 ET (C)