Physics Photo of the Week

November 19, 2010

The Pleiades - Photo assisted by Max Hunt and Alex Blume (Contemporary Astronomy
Discussion by Casey MacMillan

The Pleiades, also known as the Seven Sisters and M45, is an open star cluster, a group of stars that were formed from the same giant molecular cloud. Giant molecular clouds are enormous assemblages of molecular gas with masses of 104–106 times the mass of the sun (Comins, N, & Kaufmann, W., 2008).

The Pleiades is seen naked eye, and is visible in the northern hemisphere from late fall into early winter. This cluster contains over 3000 stars, is about 400 light years away, and is about
13 light years across (Nemiroff, R, & Bonnell, J, 2006). The age of the Pleiades star cluster amounts to around100 million years.

There are nine main stars in the Pleiades star cluster Asterope, Taygeta, Maia, Celaeno, Electra, Merope, Atals, Pleione, and Alcyone (Gibson, S).

The negative photo at right shows the contrast of the faint stars more easily.  The photos were taken using a Digital SLR camera piggy-back mounted onto a tracking telescope. The telescope was used only to track the stars; the camera was fitted with a 300 mm focal length lens.  23 images were made with a 10 second exposure at ISO 800, f/5.6.  The 23 images were digitally stacked to produce the final image.

Nemiroff, R, & Bonnell, J. (2006, January 9). M45: the Pleiades star cluster.

Gibson, S. (n.d.). The pleiades.\

Comins, N, & Kaufmann, W. (2008). Discovering the Universe. New York, NY: W.H. Freemen and Company.

There will be no Physics Photo of the Week next week due to Thanksgiving break at Warren Wilson College.  The next Physics Photo of the Week will be published on Dec. 3, 2010.

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to 

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