The Constellation of Orion (or, look up already!)
by adminIts about this time of year that that the fine Constellation of Orion rises early enough that it can be viewed without having to stay up too late.
Orion is a favorite at Spectrum Scientifics for two reasons:
1) It is a feature-filled constellation that can actually be seen easily on a clear night, even in the heart of a city.
2) Its one of the few constellations that actually sorta looks like what it is supposed to represent.
Two days before this blog entry came up a customer in the store stated flatly that you couldn’t see anything in the night sky while you were in the city. We were able to point out that the very night before Orion was shining brightly in the sky less than a mile from Philadelphia’s center region. Even around all the 4 story brownstones and street lights you could see Orion clearly, and even make out a hint of the Orion Nebula/Trapezium.
Features of Orion
First and foremost is Orion’s distinguishing belt. Three fairly bright stars line up to form a ‘waist’ on Orion and act as an instant identifier that you are looking at Orion. Two very bright stars make up two of the opposite corners of Orion: Rigel, the sixth brightest star in the night sky located in the ‘lower-right’ side of the Orion box and the Star that brings a snicker or a smile every time an astronomer mentions it: Betelgeuse, which is the ninth brightest start in the sky and makes the ‘upper-left’ corner of Orion.
Both of these stars are actually very different from each other in composition. Betelgeuse is a Red Giant with a diameter over 900 times that of our own sun and twenty times its mass.
Rigel is actually a binary star with the main star, Rigel A, being a Supergiant shining 500 times as bright as its companion, Rigel B. Rigel A is actually 40,000 times as bright as our sun, with 17 times its mass. Rigel is technically a visual binary, meaning that you can see that there are two stars with a telescope. But because Rigel A is so much brighter than Rigel B it usually takes a larger telescope (6″ or more) to get the visual.
Rounding out, or rather squaring off Orion are the stars Saiph and Bellatrix which form the other knee and shoulder respectively.
The most impressive part of Orion is the Orion Nebula/Trapezium. With the naked eye this appears just down from between the left and center stars of the belt. This is a combination of the Orion Nebula (M42) and the Trapezium, either of which can be viewed with a small telescope. The Orion Nebula appears like a whispy cloud of ‘fluff’ depending on your telescope. The Trapezium is actually a cluster of very bright, very young stars that appear within the Orion Nebula and do a magnificent job of lighting it from the interior. For many new amateur astronomers, the Orion Nebula and Trapezium is often the first Deep Sky Object they are ever able to view with their own telescope.
Orion is also home to several other Nebulae, including M43, De Mairan’s Nebula (which appears to be almost part of the Orion Nebula). B33, the Horsehead nebula, lies just below the left star on the ‘belt’. To the right of Orion’s ‘Body’, but still within the Constellation is NGC 1788, an unnamed Reflection Nebula. NGC 2024, the Flame Nebula, sits just above the left-most star in the belt. A small quantity of other brighter nebulae are in Orion, but are so close to the Orion Nebula that to a small telescope they would seem to be a part of it, if seen at all.
Perhaps best of all is that Orion can be used as a pointed to other constellations. Going ‘up and to the right from Orion’s body one can find the Pleiades, a very large open cluster that is also visible from city skies on clear Winter nights. Also, running a line through the ‘belt’ down and to the left points to Siruis, the brightest star in the night sky.
But Orion’s true advantage is that on clear winter nights it is so visible! Even from the city. Go out on a clear winter night and find Orion in the Southern sky. Its easy to do and a great start to urban astronomy.
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