Orion, The Great Hunter

OrionThe Orion constellation is visually one of the brightest, most distinct, and most recognizable constellations in all of the night sky. It is one of the most telescopically interesting constellations as well. Associated with and following Orion from the left are Canis Major and Canis Minor, the Hunter’s greater and lesser dogs. Immediately below Orion’s feet Lepus, the hare, flees the two dogs.

Once found for the first time, Orion is immediately recognizable on sight for a lifetime. It is rather well placed high in the southern sky right after sunset in February and March, located just south (below) a direct imaginary line drawn between Gemini and Taurus. Orion can be seen ascending in the eastern sky a few hours after sunset in December and January, and it can be seen setting in the western sky a few hours after sunset in April and May. The three almost equally spaced and almost perfectly aligned belt stars of almost equal brightness are likely to be the first thing noticed once an observer knows when and where to look. After finding the belt, identify the bright the stars outlining the torso, and be sure to look more closely for the dimmer stars that comprise Orion’s club and shield on either side of his torso. And finally, his dagger hangs below the left end of the belt stars. Within the dagger is The Great Orion Nebula, a reddish fuzzy blob that can be seen with the unaided eye.

As evidence that Orion attracted much of the ancient astronomers’ attention, this constellation has many named stars. Forming the head and shoulders are Betelgeuse (Alpha Orionis), Meissa, and Bellatrix. The belt is formed of Alnitak, Alnilam, and Mintaka, and marking the ends of the legs are Saiph and Rigel. Learn these names and point the stars out to friends that you wish to impress!

The deep sky objects is where Orion_Head_to_Toethis constellation gets really interesting. All of the nebulae in Orion are part of the Orion Molecular Cloud Complex, which is over 1,500 light-years away and is several hundred light years across. The Complex is as large as the Orion constellation itself, but is too dim to see except in deep exposure astrophotographs. This is one of the most intense star forming regions that we can see from Earth, containing both young stars and protoplanetary disks. Much of this region is bright in the infrared region of the spectrum due to the intense heat generated by star forming processes. Barnard_33The largest component of the Cloud, Barnard’s Loop, begins just below Orion’s right shoulder, loops toward the left above and around the belt, and ends at Orion’s right foot. the Horsehead Nebula, the Flame Nebula and the Running Man Nebula are among the most notable non-Messier nebulae in the Complex. The Great Orion Nebula (M42), perhaps the most famous Messier object of all, is located in the dagger suspended below the left end of Orion’s belt.  While visible with the unaided eye, this star forming region is increasingly more stunning through binoculars and telescope, and is an exceptional photographic object. Picture saved with settings embedded.Providing much of  M42’s illumination is a tight star cluster known as the Trapezium, which is usually photographically over saturated in  the center in order to capture the nebula’s fainter detail at its periphery. The four-star trapezoidal asterism is easily within reach of small telescopes, but the cluster actually consists of about eight stars. This little jewel is really neat to see at the eyepiece of a small telescope. Other Messier objects in the Cloud Complex are M43 and M78.

IAU Orion chart, IAU and Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 5, 2011.

© James R. Johnson, 2014.

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