Astr112 Photography Projects, Fall 2007

ET Cluster (NGC 457), Chris Kostelec

NGC 457, first discovered by William Herschel in 1787, is an open star cluster in the Cassiopeia constellation about 9000 light-years away. An open star cluster is a cluster of up to a few thousand stars that came from the same giant molecular cloud (large interstellar gas cloud). Open clusters are only found in spiral or irregular galaxies, where active star formation is taking place. It is also known as the Owl Cluster or ET Cluster, due to the fact people that it looks like an owl, or ET from the movie (the bright stars are the two eyes). The cluster contains around 100 stars total, the rest are either foreground or background stars.

The linear size of NGC 457 is 20 x 30 lightyears The stars are mostly red, white, or very light blue. Red stars are cooler stars, blue stars are hotter stars, and white stars being in the middle. NGC 457 has a magnitude of 6.4, making it one of the brightest clusters in Cassiopeia.

References:
"NGC 457 - Open Cluster in Cassiopeia" NightSkyInfo. <http://www.nightskyinfo.com/archive/ngc457_open_cluster/>

"Deepsky top 100: NGC 457 (Owl cluster, ET cluster)" Backyard Astronomy. <http://www.backyard-astro.com/deepsky/top100/14.html>