[an error occurred while processing this directive]
Calvin Observatory
Weather Forecast
Cool Images
Observing Request
External Links
Related Links
Wildrik Botjes Planetarium
Physics & Astronomy Department

Astr110 Photography Projects, Spring 2010

Previous imageUp to Astr110 IndexNext image

Alnilam ,Teresa Lubbers


The above photo is of Alnilam, the middle star of the three stars that make up The Belt of Orion. Alnilam is also the brightest of these three stars and is the fourth brightest star in all of the constellation Orion. While Alnilam is also the brightest of the belt stars, it is also the farthest away - 470 light years farther away from Earth than the other two stars (Alnilam is 1,340 light years from Earth). Alnilam is so bright because it is a blue super giant, which is a very immense and hot star, bigger than our Sun. Alnilam is also bright enough for its reflection to make visible a nearby cloud of interstellar dust and gas, also known as a reflection nebula. In this case the nebula that can be seen because of Alnilam's light is called NGC1990.

The above image of Alnilam has a blue hue due to the nature of Alnilam as a blue super giant. Alnilam appears much bigger than the surrounding stars in the image due to the magnitude and brightness of the star. Because the star has such a high magnitude in the extended length of this particular exposure, it exposed many more pixels around the actual star. So the high number of exposed pixels in the star is not due to an abnormally large diameter but rather to a large magnitude.


Kaler, Jim. "Alnilam." Astronomy Picture of The Day. <http://stars.astro.illinois.edu/sow/alnilam.html>.

Fisher, Mark. "Alnilam."eSky The Electronic Sky. <http://www.glyphweb.com/esky/stars/alnilam.html>

Right Ascension (J2000) '05 36 44.00'
Declination (J2000) '-01 11 43.0'
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 5x60 seconds in C, 300 seconds in BVR
Date and time observed

March 3, 2010 at 22:33:17' (10:33:17 pm)