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Astr110 Photography Projects, Fall 2004

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NGC 281, Sierra Yazzie

Helix Nebula

NGC281, also known as the Pacman Nebula, is a faint nebula surrounding an open star cluster in the Cassiopeia constellation. This is considered one of the most beautiful star fields in the sky. Its large size makes it a great target for astro-photography. NCG281, like many other ionization nebulae, appears red because the hydrogen electrons are dropping from energy level 3 to energy level 2, emitting red spectral lines. Open star clusters like the one pictured within the Pacman nebula are found only in the disks of galaxies, and often contain much younger stars.

In this particular photograph, the bottom right section of the nebula has very visible edges, this is due to clouds of dust in the way of the light. Stars in this cluster have a bluer tone because they are younger, and therefore warmer in temperature. The brightest star in the center of the cluster is known as GSC 3663;1231, and has 7.4 magnitude. This nebula would be found in the disk of the Milky Way, but could only be viewed with the aid of a telescope.

Bennett, Donahue, Schneider, Voit, The Cosmic Perspective. Addison Wesley, 2002.



Right Ascension (J2000) 00:52.8
Declination (J2000) 56:36
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 300 seconds in all filters

November 2, 2004, (BV)
November 4, 2004, (C)

November 30, 2004 (R)