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Dumbbell Nebula (NGC 6853) & Skull Nebula (NGC 246)
Jenna Diephouse & Jana Zondervan

Helix Nebula Orion Nebula
Dumbbell Nebula- Jenna Diephouse Skull Nebula- Jana Zondervan

The Dumbbell and Skull Nebulae are both planetary nebulae. A plantary nebula is one of the last stages in the death of a low-mass star. When the dying star sheds its outer layers, the core is exposed, and the outer layes become a large shell of gas. The core remains extremely hot and emits ultraviolet radiation. This radiation makes the gas shine different colors, which we call a planetary nebula.

NGC 6853, or the Dumbbell Nebula, is a planetary nebula thought to be about 1,200 light years away. It was discovered by the French astronomer Charles Messier in 1764, and is around a half light year in diameter. As seen in the sky, it appears about half the size of the full moon and is found in the Vulpecula constellation. The green-blue that appears in the image of the nebula denotes oxygen atoms while the red edging shows hydrogen. It is estimated that NGC 6853 became a nebula from a red giant star 4,000 years ago, and will probably become unable to see in the next 10,000 years. It will disappear like this because a planetary nebula, as a collection of hot gas, gradually cools and spreads out into space. The Dumbbell Nebula's central star is a large white dwarf--5.5% the width of the Sun--and is hot: 85,000 Kelvin. This dwarf star's UV rays heat the atoms of the nebula, making them give off their colors.

The Skull Nebula is about 1,600 light years away from us in the constellation Cetus. It lies in an area of Cetus where other stars are fairly scarce. This particular planetary nebula was discovered in the 1785 by William Herschel, the same astronomer who discovered Uranus. You can recognize it by its blue outer ring which is brighter on the eastern side than the western. The nebula seems to be moving in that same direction. The combination of this nebula’s interesting direction and structure is thought to be due to shock waves that are caused by stellar wind. These rings/shock waves gave the nebula its name, the Skull Nebula. While the Skull Nebula is a planetary nebula, it is different from most in a number of ways. It is smaller and dimmer than most, and for these reasons, it is often a bit difficult to see. It is only two and a half light years in diameter and its magnitude is 10.9. However, unlike the nebula itself, its central star is more noteworthy. It is a PG1159 white dwarf, and it is one of the hottest known at 200,000 degrees Celsius. It is likely all that’s left of a Wolf Rayet-type central star.

As previously stated, both of these nebulae are planetary nebulae, and they both have a white dwarf as their central star. Planetary nebulae are called "planetary" because when they were discovered, they were small and round like planets.

The Dumbbell Nebula is green, blue, and red, revealing that oxygen and hydrogen are present, while the Skull Nebula is known for its blue ring caused by shock waves from stellar winds. The Skull Nebula is bigger than the Dumbbell Nebula by about two light years in diameter, but it is much dimmer than the Dumbbell Nebula by a magnitude of 3.5.

References:

European Southern Observatory. Web. 4 Dec. 2015. <https://www.eso.org/public/images/eso9846a/>.
Bennett, Jeffrey O., Megan Donahue, and Nicholas Schneider. The Cosmic Perspective Fundamentals. San Francisco: Pearson Addison-Wesley, 2010. Print.


Brazell, Owen. "Deep Sky Challenge: Skull Nebula." Astronomy Now. 9 Oct. 2014. Web. 4 Dec. 2015. <http://astronomynow.com/2014/10/09/deep-sky-challenge-skull-nebula/>.


GaBany, R Jay. "The Dumbbell Nebula." (NGC 6853, M27). 2011. Web. 20 Nov. 2015. <http://www.cosmotography.com/images/small_ngc6853.html>.


"Messier 27: Dumbbell Nebula." Messier Objects. 2015. Web. 4 Dec. 2015. <http://www.messier-objects.com/messier-27-dumbbell-nebula/>.


"Skull Nebula (NGC 246)." Skull Nebula (NGC 246). The World's of David Darling. Web. 4 Dec. 2015. <http://www.daviddarling.info/encyclopedia/S/Skull_Nebula.html>.


"Skull Nebula, NGC 246." Skull Nebula, NGC 246. Web. 20 Nov. 2015. <http://www.astrophotolab.com/pr/n0413sp.htm>.


"The Not-so-Ordinary Life of a Typical Star." Formation of Planetary Nebulae. Web. 4 Dec. 2015. <http://www.cosmotography.com/images/planetary_nebula_formation.html#dumbbell>.

 

Object Dumbbell Nebula Skull Nebula
Right Ascension (J2000) 19:59:36 00:47:03
Declination (J2000) +22:43:18 -11:52:17
Filters used B (Blue), C (Clear), R (Red), V (Green) B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter C (210s x 2); B (195s x 2); V and R (90s x 2) C and B (500s); V (150s); R (120s)
Image dimension 773x558 pixels; 16.75x16.12.09 arc minutes 308x343 pixels; 6.67x7.43 arc minutes
Date/time observed October 01, 2015, 07:04 UT October 02, 2015, 05:51 UT

 

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