Physics Photo of the Week

January 23, 2009

Orion Nebula - Discussion by Molly Herold
Photos by Brent Figlestahler and Donald Collins

These photos of the Orion Nebula were taken from just outside Spidel on the evening of December 3rd, 2008. The object was photographed with and with out an H-alpha filter.  Several pictures were taken at a 4 second time exposure. The photos were then stacked the on top of one another to reduce noise. The images were adjusted in terms of contrast and brightness to enhance the view of the Nebulous cloud.

The Orion Nebula can be seen with the naked eye and is seen as a smudged star just below Orion’s belt. The Nebula is made up of several hot, bright young stars that are surrounded by a cloud of dust and gas. The massive size of this object is actualized when you consider it is several light years wide itself.  The angular size of the complete nebula is more then 4 times the area of the full moon. This deep sky object is actually part of an even larger structure known as the Orion Molecular Cloud Complex which includes the Horsehead Nebula, M34, the Flame Nebula and Barnard’s Loop.

When photographed with a color camera, the Nebula can be seen in an astonishing array of Blue, Red and Green all caused by reflective radiation of stars in the core. Using the H-alpha filter in this second image we are allowed to see only a small band of emission from the object - the hydrogen spectra. This is helpful because it allows us to see the cloud of the Nebula with greater clarity, since it is made up of about 90% hydrogen.  The H-alpha filter suppresses the images of the stars because the stars are mostly incandescent sources, whereas the nebula has most of its light concentrated in the H-alpha color.

Watch for color images of the Orion Nebula to be made by students in Earth, Light,and Sky.

[Note: Molly Herold and Brent Figlestahler both completed Contemporary Astronomy in the fall 2008 semester.]

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an 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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