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Astr112 Photography Projects, Fall 2007

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E. T. Cluster, Jillie Wowk-Kennedy

ET Cluster

NGC 457, or the ET Cluster, is what is known as an open star cluster (a group of stars usually numbering in the thousands that formed from the same interstellar cloud). The ET Cluster gets its name from the popular movie character. The two brightest stars look like eyes (lower left-hand corner), the elongated shape of the cluster makes up the 'body' and wide-spread 'arms,' while the bright stars at the 'bottom' form the 'feet' (upper right-hand corner). It has also been called the Owl Cluster because the arms could double as outstretched wings. It's not hard to imagine the eyes as big owl eyes. This rich cluster is found in the northern constellation Cassiopeia and can be seen during the autumn months. It was discovered in 1787 by William Herschel, the British astronomer who also discovered Uranus.

One of the bright stars you see in the center of the cluster, Phi Cassiopeiae, is not actually a part of the ET Cluster, but is still found in the constellation Cassiopeia. This star is in its super giant stage, which explains why it's so luminous. The bigger, high mass stars that you see are mostly hot, blue stars. These stars are primarily found in the lower left corner of the picture, towards the 'eyes.'But because this is a deep photo most of the stars we see are cool, low-mass stars. The cluster's linear size is roughly 30 light years.


"Deepsky Top-100 (14): NGC 457." Backyard-astro.com: Backyard Astronomy for Amateur Astronomers. <http://www.backyard-astro.com/deepsky/top100/14.html>

Neata, Emil. "NGC 457 - Open Cluster in Cassiopeia." Night Sky Info. <http://www.nightskyinfo.com/archive/ngc457_open_cluster/>.

"Phi Cassiopeiae." Wikipedia. <http://en.wikipedia.org/wiki/Phi_Cassiopeiae>.

"William Herschel." Wikipedia. <http://en.wikipedia.org/wiki/William_Herschel>.

Right Ascension (J2000) 01:19:37
Declination (J2000) 58:20:50
Filters used clear(C)
Exposure time per filter 10x30 seconds in C
Date observed

October 17, 2007 (C)