Many nebulae — large collections of gas within our Milky Way galaxy — acquire common names because they look vaguely like some familiar object, but often it takes a bit of imagination to see a familiar object in the swirl of gas. One exception is the Horsehead Nebula, which actually looks a lot like a horse’s head. Because of this it is one of the most beautiful and most photographed of all objects in the sky. Because it is rather faint, it normally takes a long time exposure to show it well. And because it is in the constellation of Orion, which is visible mostly in the winter, it is usually quite cold when trying to photograph it. I have been trying for many years to get a decent picture for myself, but some glitch or other has always occurred. Finally, however, I was able to get a picture that I am satisfied with, and I wanted to share it with you. (Please see attached file.)
The Horsehead Nebula (technically known as Barnard 33) is a dark nebula that obscures part of the red emission nebula (known as IC434). This nebulosity is located just south of the star Zeta Orionis, which is the easternmost of the three stars that make up Orion’s belt. A nearby star, Sigma Orionis, provides the strong ultraviolet light energy that causes the hydrogen gas in IC434 to glow red. Neither of these stars is in the field of view of this photograph. The bright blue nebula near the lower left corner is known as NCG 2023. It is a reflection nebula, reflecting the blue light of a star embedded in it. The dark clouds of dust and gas that make up the Horsehead Nebula and the surrounding region are areas where new stars are actively forming. It is about 1500 light years away, which means the width of the horse’s neck is a little over one light year across. If you were to place in the Horsehead Nebula a circle the size of the earth’s orbit around the sun, it would take more than 36,000 of those circles to fill the distance across the horse’s neck!
Technical information: This image, a composite of 44 2-minute exposures at f/7 using an 11-inch diameter telescope, was completed just before dawn on September 22, 2012. The width of the image is about 2/3 of a degree and the height is a little less than 1/2 of a degree, so the total area of sky covered is just slightly more that the area of the full moon. North is to the left.
I hope you take a moment to enjoy this picture and reflect on the size of our world compared with the amazing objects that inhabit our Milky Way galaxy.
Keep looking up,
Carter Mehl,
(Sometime) Resident Astronomer,
Lookout Observatory
