Orion

by Shaphan Shank | Feb 1, 2024 | 0 comments

Horsehead Nebula
Horsehead Nebula. Photo © Kevin & Adrian Shank.

Orion, the Hunter, is one of the most well-known constellations in the night sky. Most of its popularity comes from the fact that it is made up almost exclusively of bright stars and has an easily recognizable shape, a combination that most other constellations don’t have. February is one of the best months for observing objects around Orion. This month, the Hunter is near the meridian during the evening hours.

By far the most fascinating telescopic target in Orion is M42, the Orion Nebula. This nebula is the middle “star” in Orion’s sword. A binocular will clearly show that this is no star. To really appreciate this nebula, though, you need to see it through a telescope of reasonably good quality. With any good telescope, the Orion Nebula becomes a beautiful cloud of glowing gas. Look at this nebula through a large telescope, and you won’t soon forget it. There are too many tendrils and curtains of glowing nebulosity to describe the view easily; you have to see it. Keep in mind that you won’t see the spectacular colors seen in photographs of the Orion Nebula. Most of this color is too faint for us to see and/or it is a wavelength of light that our eyes do not detect. The nebula will appear gray, perhaps with a slight tinge of green or pink.

Embedded in the heart of the Orion Nebula is a tiny group of stars called the Trapezium. The Trapezium consists of four stars that are easily seen, plus a handful more that are difficult to observe. A good telescope should be able to resolve the four main stars of the Trapezium.

There are several other interesting objects in Orion, although they might get more attention if they were a greater distance from M42. NGC 2169 is one example. Also known as the “37 cluster,” this is an open star cluster in the northern part of Orion. NGC 2169 gets its popular name from the shape of two chains of stars that make up most of the cluster. These chains of stars bear a fascinating resemblance to the number 37. To find this star cluster, follow Orion’s club up from Betelgeuse until you get to the first east-west pair of stars in the club. NGC 2169 forms an (almost) equilateral triangle with these two stars, on the south side of them. Although it is bright, this cluster is much too small to be a good binocular target.

Besides the Trapezium, Orion contains several other interesting multiple stars. Sigma Orionis is a quadruple star located about a degree southwest of Alnitak. Hatsya, the bottom star of Orion’s sword, is a triple star. Hatsya is in a “busy” field of view, which contains some nebulosity from the M42 complex and a star cluster with several double stars.

Orion also has an extraordinary amount of nebulosity. Much of this nebulosity is too faint to allow for easy telescopic observation. If you think (like I do) that any nebulosity is interesting, even if it is faint and challenging to see, then Orion will keep you busy for a while, provided you have access to a mid-sized telescope and fairly dark skies. Otherwise, M42 will probably be the only nebula of interest in Orion.

If you have been interested in astronomy for very long, chances are you’ve seen photos of the Horsehead Nebula. This nebula’s distinctive shape intrigued me from the first time I saw a photo of it, and, like most other stargazers, I’ve wanted to see it for years. However, the Horsehead is quite difficult to observe. As with most difficult objects, a large-aperture telescope, a dark sky, and experience all help a lot in observing this nebula. A Hydrogen-beta filter is also very helpful when observing the Horsehead. This nebula is less than one degree south of Alnitak, the eastern star in Orion’s belt. The Flame Nebula, which is about a quarter degree east of Alnitak, is also rather faint, but it is much easier to see than is the Horsehead.

star map of Orion

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