Astr110 Photography Projects, Fall 2004

Blue Snowball, Nicholas Cunigan

This is the Blue Snowball. Discovered in 1784 by William Herschel it is a planetary nebula found in the Andromeda Galaxy. Surprisingly enough our own sun will one day look like this. In 5 billion years the Sun will throw off its outer layers and go through a planetary nebula phase. This occurs when gravity compresses the stellar core to high temperatures. Soon thereafter the star will become a white dwarf and the high temperatures will cause the expulsion of the star's outer layers, creating a planetary nebula, such as the Blue Snowball--also known as NGC 7662. This object is 4,000 light years from the Earth and is moving towards our solar system at a speed of 13 km/sec and is expanding at a rate of 26 km/sec.

This image has been color enhanced to show off the blue color that was skewed by over exposure. The normal picture of the planetary nebula would show red FLIERs (pairs of low ionization knots which lie near the symmetry axis of many planetary nebulae) and a greenish white glow permeating from the center. These colors are the gases that are pushed away at the time of expulsion and represent the mass of the original star. Much is still to be learned about planetary nebulas including what exactly these FLIERs consist of and the details of the physical mechanism that creates the nebula.

References:
http://www.astro.washington.edu/balick/WFPC2/n7662.caption.html

http://technet.gtcc.cc.nc.us/comserv/cline/snowball.htm

http://antwrp.gsfc.nasa.gov/apod/ap961121.html