Astr112 Photography Projects, Spring 2006

Clown Face Nebula (NGC 2392), Clara Campbell

The Clown Face Nebula, also known as the Eskimo Nebula, was discovered by William Herschel on January 17, 1787. It is a relatively bright planetary nebula (which is material thrown off by a star that has run out of hydrogen fuel to burn) located in the constellation Gemini, and is estimated to be some 3000 light years away. It is bluish in color and appears to blink on and off as the viewer uses averted vision.

In the interest of further clarification on what a planetary nebula is: it is "an expanding envelope of rarefied ionized gas surrounding a hot white dwarf (a dying star). The envelope receives ultraviolet radiation from the central star and reemits it as visible light by the process of fluorescence. The planetary nebula stage lasts less than 50,000 years. During the core contraction that terminates the red giant stage, the helium-burning shell is ejected at a velocity so high that it becomes separated from the core" (Astronomy Knowledge, www.site.uttowa.ca) By my calculations, the nebula is about 3.5 light years in size. The Clown Face Nebula particularly displays this ejection of the former shell: in fact, one can see two layers surrounding the small white dwarf in the center when viewing a photograph of higher resolution. The first 'envelope' is more bluish in color, swirling around the core, which is what is primarily visible to us on Earth. With a higher resolution, one can see inner filaments (more orange in coloring) being ejected by strong winds of particle from the central star. From the Hubble Space Telescope, the Clown Face Nebula displays gas clouds so complex they are still not fully understood.

References:
http://www.seds.org/~spider/spider/Misc/n2392.html

http://www.skynewsmagazine.com/pages/pow_archivelist23.html

http://www.site.uottawa.ca:4321/astronomy/index.html#planetary nebula

http://antwrp.gsfc.nasa.gov/apod/ap031207.html