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Physics & Astronomy Department

Astr111 Photography Projects, Fall 2009

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Open Cluster NGC 744 (Perseus), Katie Hall

Open Cluster

Open clusters such as the Pleiades (M45) and the Hyades have been under observation since prehistoric times.  Thought to be nebula until 1609 when Galileo discovered their composition to be that of stars, open clusters are often bright and visible, even with the most rudimentary of telescopes.  Unlike globular clusters, which contain several million stars that can hardly be differentiated, open clusters may contain 50-1000 stars, which are typically much younger. They can be found in the disk of the galaxy (the plane in which the spirals, bars and discs of disc galaxies exist)

It can be assumed that a group of stars that are close together in space held together by gravity came into existence from the same cloud with the same composition at nearly the same time. What does that mean?  This makes open clusters interesting for astrophysicists, because stars at almost the same distance have approximately the same age and chemical composition. Since they also have different masses, this allows a cluster to present with a broad range of stellar evolutionary stages.

Scientists would assume that most stars in the above image are approximately the same age, but these stars have different masses and temperature.  The more massive stars are red and cooler, while the small and blue and hotter.  Since the stratification of colors is present, we can infer that this is a young cluster.  If it was older, the brighter red stars would have exhausted their fuel.  The cluster is rich in stars on the left side of the photo and has a magnitude of 7.9.  The distance is 4890 light years and its linear size, 2.95 light years.  And, it is located just inside the border of Perseus from Cassiopeia. 

References:

Andrew Fraknoi, David Morrison, Sidney Wolff. To the Stars and Galaxies.
Saunders College Publishing, 2000. Pg 272-274.

Fromert, Hartmut and Kronberg, Christine.  “Open Star Clusters” Students for the Exploration and Development of Space. August 2007. http://seds.org/MESSIER/open.html

NCKAS – Open Clusters. “North Central Kansas Astronomical Society.” 2005. http://www.nckas.org/openclusters/

Right Ascension (J2000) 01:58:24.0
Declination (J2000) 55:29:00
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 5 x 10 s.
Date observed

November 11, 2009