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Astr111 Photography Projects, Fall 2005

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Little Dumbbell Nebula, Renee Meadors

Little Dumbbell Nebula

The planetary nebula M76, also known as the Little Dumbbell Nebula, is located in the extreme western portion of the constellation of Perseus about 3400 light years away. When it was first discovered on September 5, 1780 by Pierre Mechain, the Little Dumbbell Nebula was thought to be a nebula without stars, but correctly identified later as a planetary nebula in 1918 by Heber Curtis. Planetary nebulas, in fact, have little to do with actual planets. The name comes from their similarity in appearance to gas giant planets. Planetary nebulas are the final stage in stellar evolution, and are generally faint objects that can't be seen by the naked eye. Formed by certain types of stars at the end of their lives, they consist of a shell of glowing gas and plasma, and tend to be a short-lived phenomenon, lasting only a few tens of thousands of years.

The appearance of the Little Dumbbell Nebula resembles a butterfly because of the cloud hovering around the central star. This adds to its list of names Butterfly Nebula, as well as Cork Nebula, and Barbell Nebula. The main body is a bright, slightly elliptical ring, which is about 65 arc seconds in diameter. Although it is seen as yellow in the picture, the central star is blue, due to its temperature being increasingly hot. The star is yellow in the picture due to complications on behalf of the program used to color it. The expanding cloud of gas becomes visible once the hot core of the star is exposed and the high-energy, ultraviolet light from the core causes the cloud to fluoresce. This halo surrounding the bright star consists of a material that was ejected by the central star in the form of stellar winds while it was in its Red Giant phase, and covers a region of 290 arc seconds in diameter. The cause of the halo is uncertain, however, the hypothesis seems to be that the magnetic field and spin of the central star are channeling the gas. As seen in the picture above, the nebula is of a greenish color. This is due to the fact that the visual light is emitted in the spectral line of the green 5007 Angstrom forbidden line of doubly ionized oxygen. Since the oxygen has been doubly ionized, it has lost two electrons. Therefore, it can pick up on wavelengths and celestial objects in the 500 nm spectrum. Simply put, it is best seen in the green part of the spectrum.

References:
http://www.seds.org/messier/m/m076.html , The Messier Catalog

http://encyclopedia.thefreedictionary.com/planetary+nebula , The Free Dictionary

 

 

Right Ascension (J2000) 01:42.4
Declination (J2000) +51:34
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 300 seconds in BVR and clear
Date observed

October 6, 2005 (C)
October 7, 2005 (VR)

October 11, 2005 (B)