By Daniel Acker
The 1988 movie and now cult classic, Beetlejuice, is where most people will recognize this name from. However, the origin of the name is quite a bit older, and derives from the Arabic term bat al-jawzā, or “the giant’s shoulder”. It is also known as Alpha Orionis, and aside from being part of a funny movie and having an oft-mispronounced name, this star is part of a constellation that offers some fantastic stargazing in the winter months of January, February and March for the northern hemisphere. Below are some of the best options for viewing as well as some details about the stars that make up Orion and how to view them.
Alpha Orionis – Betelgeuse
At 425 light-years distant, Betelgeuse is one of the most luminous stars known and is the seventh brightest star in the northern hemisphere. This star is a red supergiant of spectral class M2lab with an apparent visual magnitude of 0.42 and is also one of the largest stars known, about 1500 times the diameter of our Sun. If we could place Betelgeuse where our Sun is, it would fill the orbits of the planets out to Mars and possibly Jupiter. One additional interesting fact, Betelgeuse is a semiregular pulsating variable star first noticed by Sir John Herschel in 1836. When at maximum, Betelgeuse sometimes rises to magnitude 0.4 when it rivals the star Rigel (Beta Orionis). It is important to note here that this “rise” in magnitude is rare so unless you watch this star, you may just miss the next outburst. Looking at Betelgeuse through binoculars or a telescope, the star appears vivid orange instead of red as you may expect.
Beta Orionis – Rigel
Rigel is the brightest star in the constellation Orion and even though it doesn’t have the alpha designation, it is almost always brighter then Betelgeuse. At 85,000 times the luminosity of the Sun and containing 17 solar masses, Rigel is a blue supergiant of spectral class B8. In binoculars or telescope, Rigel appears blue-white in color. Rigel is really a star system composed of three stars. With a telescope of 150mm (6 inches) and larger, you should be able to detect the 6.7 magnitude companion just 9” (arc-seconds) from Rigel in position angle 202°. To split the double you may need to use medium to high power, say around 125x or so. This star, Rigel B, is itself a spectroscopic double (meaning it’s too close to be split in a telescope). The pair shows no orbital motion but is believed to be physically related because they exhibit the same radial velocity. An interesting thought to ponder while observing this star system is that Rigel A seems to be losing some material, puffing it off (although some falls back) with a period of about 22 days.
Lambda Orionis – Double Star
Lambda Orionis marks the head of Orion and forms a triangle with the two forth magnitude stars Phi-1 and Phi-2. With the 90mm refractor at 100x the close AB pair are split enough to see the two stars but increasing the power to 150x easily resolves the pair. The AB pair is separated by 4.40” arc-seconds and shines at magnitudes 3.7 and 5.6 respectively and appears white. Larger telescopes may show two additional stars to this system. The 11.2 magnitude C star at 28.6” in position angle 184° and the 11.2 magnitude D star at 78.3” in position angle 271°.
Iota Orionis – Double Star
Iota Orionis is really a triple star with a white primary at magnitude 2.9 and a blue secondary 11” away in position angle 141° glowing at magnitude 7.0. I was able to split the pair with the 90mm refractor using 100xpower. The third component, a reddish 11th magnitude star is located 50” away in position angle 103°. If you’re using a larger telescope and are lucky enough to be away from light pollution, you may be able to detect the large but faint nebulosity of NGC 1980 that surrounds Iota Orionis.
Zeta Orionis – Double Star
Zeta Orionis is in a relatively bright field of several emission and reflection nebula. About 15’ arcminutes east of Zeta is the emission nebula NGC 2024 and extending south from Zeta is the 1° long reef of IC 434 which is a faint glow that has the famous Horsehead Nebula silhouetted against it. Unless you’re located at a very dark site with a large telescope, you’re not likely to see any of the nebulosity but, Zeta Orionis is an easy split in a small telescope. With the 90mm refractor at 65x power, Zeta resolves into a pair of blue-white stars of magnitude 2.0 and 4.2 respectively, separated by 2.6” in position angle 162°.
M42 and the Trapezium
A familiar deep sky object to beginners and experienced observers alike is M42, The Great Orion Nebula. Visible to the naked eye as a fuzzy patch around Theta Orionis. You may recognize it as the middle star in the Sword of Orion. Theta Orionis itself is a wide double separated by 135”. The western component of which Theta-One Orionis is the famous Trapezium. A 90mm telescope will show the four stars that make up the trapezium, but larger scopes reveal many more stars in the system. The Trapezium is just a small part of a larger open cluster. Okay, let’s talk about M42. M42 is an emission nebula visible to mid-northern hemisphere observers. M42 can been viewed through binoculars or small telescopes even under light polluted skies. One of my observations from 19 January 2010 says, “I guess I’ll never be able to describe M42 with any real detail. The view with the 150mm refractor at 54x is just amazing! The Trapezium is ablaze, and I can see mottling across the entire object. At 108x M42 is truly breathtaking!”
So, even if the Moon is big bright you can still explore some of the interesting stars and double stars Orion has to offer. You don’t need the darkest skies or the clearest skies and many can be observed from your backyard under moderate light pollution and less than transparent skies. You don’t need large, expensive telescopes, a small refractor, Newtonian reflector, or Schmidt-Cassegrain will do just fine using magnifications between 75X and 150X. We like to hear from our readers about their observations too. So, drop us a line and tell us what you see from your backyard.
Clear Skies!
Sources:
https://www.britannica.com/place/Betelgeuse-star
Orion’s stars and double stars and M42 from my personal observations and logbook notes.