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Physics & Astronomy Department

Astr110 Photography Projects, Spring 2008

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Owl Nebula (M97), Mike Ludema

The Owl Nebula is a planetary nebula (that is to say a cloud of ionized gas and plasma that is formed by certain stars when they die), that is located in the Ursa Major constellation (the region of the sky in which the big dipper can be seen). It was discovered on February 16, 1781 by a french scientist named Pierre Méchain, but was not classified as a planetary nebula until 1844. It was not until 1848 that Lord Rosse came up with the apt title of "the Owl Nebula."

Com paired to many other stellar objects the Owl Nebula is a relatively faint, with a magnitude of only 9.9. Its distance is somewhat disputed, but the Messiar Object Index places it at roughly 2,600 ly and has the angular size of 3.4 x 3.3 arc min. Assuming that the Messiar number is correct, the actual diameter of the Owl Nebula is only about 3 ly (as a comparison consider that the Milky Way is 100,000 ly in diameter). The star at the center of the nebula has a mass that is slightly smaller than our sun (about 1/7th) and the nebula itself is believed to have been formed 6,000 years ago.

As one can see from the picture, the Owl Nebula is a very complex heavenly object. The theory as to why the Owl Nebula looks the way it does is that its shape is a globe which has had its poles chopped off. This means that because of our perspective the we are looking though less gas at the spots where the poles would be, which results in the dimmer "eye" sections. Surrounding the main body of the nebula, there is a fainter red nebula made up of a gas of lower ionization. This layer is only faintly visible in the above picture as a slight red strip outlining the main green body.

References:
Messiar Object Index. "Messier 97." http://www.seds.org/messier/m/m097.html

Right Ascension (J2000) 11:14:48
Declination (J2000) +55:01:00
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 1x3 minuets in BVR and C
Date observed

April 1, 2009 (BVRC)