Stockton Astronomical Society
Valley Skies - January 2000 Issue
Constellations:
Orion the Hunter
Gen: Orionis
Abb: Ori
Dec: -11.0° to +23.0°
RA: 4 hr 41 min to 6 hr 23 min
Area covered: 594 square degrees
Orion is often times referred to as the master of the winter skies. He can be found rising in the east during late fall, traveling across the sky all winter long and is still visible in the west during the early spring. Next to the Big Dipper, Orion is probably one of the most familiar asterisms in the sky. One of the reasons that Orion is so familiar is that it is one constellation that really looks like what it is called. It is easy to imagine the great hunter with his sword hanging from his belt and a club raised high over his head. Orion makes his appearance in the east late in the evening during October; he reaches the highest point in the sky during mid January, and sets with the sun in late march.
The belt of Orion, formed by three stars (from west to east, Mintaka Delta Ori, Alnilam Epsilon Ori, and Alnitak Zeta Ori) equally spaced and approximately the same magnitude, is probably the first thing to catch the eye when you look up in the winter sky. These three stars have been known and used throughout history by just about every culture that has ever existed on Earth. Even before the Lunar calendar, these three stars where used to mark the passage of time during the winter months. In cave paintings found in France the three stars showed that when Zeta was down at the bottom of the vertical line winter began; when the line was horizontal winter was half over and, as Zeta rose high, spring was on it's way. The three stars were also used by the early Japanese to determine the times to plant and harvest the two main crops, rice and millet. In Japan, long before Chinese influence, the three stars where known as Mitsu Boshi a kind of fulcrum with rice at one end (Zeta Ori) known as Komeinya Boshi and millet (Delta Ori) Awainya Boshi. When Zeta was down it was time to harvest the rice and plant the millet and when Delta was down it was time to harvest the millet and plant rice.
Since the stars that make up Orion have been seen and used together for so long, there have been literally hundreds of legends and myths passed down, century after century, by almost every culture in the world. During my search for information this month I found over sixty different myths, some of them having several different variations. The constellation of Orion has been seen as a dweller of the mountain (early Indians), a hunter (Greek), a warrior (Sumerians), a hero (Samoan), a god (Egyptian), a drum (early Japan), and a young girl carrying water (China) just to name a few. Even the Bible makes reference to this constellation, when God reportedly came to Job and, to show how all-powerful he was, asked Job if he was able to "loose the bands of Orion" (Job 38.31).
Greek mythology has many versions with at least four major versions of how Orion was brought into this world. One version of Orion's life goes like this:
He was born the sun of Poseidon and Euryale. He grew up to be a great hunter -- so good of a hunter that he once boasted that he could kill all the animals on the Earth. After hearing this, the Goddess of the Earth sent a scorpion to kill Orion. Orion soon learned that he was not going to be able to win this battle, jumped into the sea and tried to reach Delos. Apollo watched over the battle. Since he hated Orion for trying to seduce his sister Artemis, Apollo was not going to let Orion get away. He tricked his sister by challenging her to hit the black spot far out to sea. Artemis was an expert shot and the arrow struck Orion in the head on the first shot. When she swam out to retrieve her arrow she realized that she had been tricked. She begged Zeus to restore Orion's life but he refused, so Artemis placed Orion in the heavens with his hunting dogs and a rabbit and a bull to hunt for all time. The scorpion is also in the sky; having never completed his mission he continues to chase his prey across the sky year after year.
Exploring in Orion
Orion has a wealth of deep sky objects to view and many of us got our start in amateur astronomy after we first looked at the area seen as Orion's sword through binoculars or a small telescope. Photographs of Orion show even more deep sky objects than can be seen through most telescopes.
To start out for this month, lets jump right to the easy hit. First look for the belt of Orion (described above) then look for the naked eye smudge of light that hangs below the belt. The brightest area is M42 (NGC 1976) "The Great Orion Nebula". M42 is a must-see object with all of its complex splendor of dark dust lanes and bright luminous filaments surrounding the "Trapezium" (theta Orionis). You can spend hours exploring this area and still have more to see later. The Trapezium has attracted astronomers since 1610; at that time telescopes only resolved three stars. With the invention of much better telescopes they can now see eleven stars in this cluster but it is believed that there are at least 30 stars associated with it. With a few of the scopes in our club it may be possible to see eight of the stars as shown in the chart below. In a couple of books that I have looked at, the reflection nebula to the north is listed as M43, when in reality M43 (NGC 1982) Is just a small part of the main nebula that appears detached by a dark dust lane.
M43 is a little under 10 arc-minutes to the northeast of the Trapezium. This nebula is classed as both an emission and a reflection nebula surrounding an 8th magnitude star. Together M42 & M43 form what is considered to be a large celestial nursery, with enough mass and material to give birth to 10,000 stars the size of our sun.
From this point it may help to look at a photograph of the area to train your eyes to see the details in the next few objects. On the southern edge of M42 is the reflection nebula NGC 1980. This nebula is fairly bright around the stars but can be easily missed in the light from M42. The primary source of the illumination for NGC 1980 is the 2.8 magnitude star 44 Iota Orionis.
Travel back north, up the sword. About ½° north of the Trapezium you will find the reflection nebulas NGC 1977, 1975 and 1973. This is the area that gets mislabeled as M43. In photographs these three nebulas are spectacular, but it takes a bit of work to get your eyes to tease out the intricate details at the scope. Just to the north, but still involved in the nebulosity, is the loose open cluster NGC 1981.
From NGC 1981 hop up to 50 Zeta Orionis, the eastern most star in Orion's belt. This area has probably been photographed by more amateur astrophotographers than any other single area in the sky. Running to the south of Zeta is the famous "Horsehead" nebula, made up of the bright nebula IC 434 and the dark nebula B 33. One of the reasons this area is so popular for photography is because it shows up very well in pictures but is all but impossible to see visually without the aid of an H Beta filter. I managed to see it once in my 10" scope, with a 27mm eyepiece and the filter. It was truly worth the effort for me, but before you run out and buy a $115 filter be warned that it is nowhere near as bright or spectacular visually as it is on film (and the H Beta filter is not as usable as, say, an 0III).
To the east of Zeta is the "Flame" nebula, NGC 2024. This one is pretty easy to pick out with an OIII filter or a UHC filter. I have read and heard several different descriptions of this nebula, such as "Christmas tree," "tank tracks," even a "skinny Africa." I think that the flame is more of a common description than a proper name. On the same night that I found the Horsehead Nebula I also checked out the Flame with the H Beta filter and it showed a lot of different detail. NGC 2024 is an emission nebula that is obscured by a dark lane dividing it down the center. Just to the south and located closer to the Horse head you may find NGC 2023, a small reflection nebula surrounding a central star (be sure to remove any filters before trying to find it). The whole area around Orion's belt is peppered with small reflection nebulae, mostly from the Index Catalogue (IC) list of deep sky objects, compiled between 1895 and 1908.
From Zeta, travel ¼ of the distance to Betelgeuse (pronounced "Bettlejuze" or "Beetle juice"), 58 Alpha Orionis, then a little over a ½° to the east to find M78 (NGC 2068). M78 appears as two stars cushioned in a nest of pale mist. This diffuse nebula shows up very well even in smaller telescopes, but is often overlooked because of its proximity to M42 and the other objects we have hit. In this same area, you may be able to pick out NGC 2064, 2067and 2071. All of these are faint diffuse nebulae (probably all part of a much larger nebula) reflecting light from the stars that appear in their centers. Continue a little under 2° east and less than ¼° north to find the open cluster NGC 2112. This cluster has a weak central area and is a bit hard to find but, once found, large scopes may show some nebulosity around the stars.
These next four objects are not for those that get discouraged easily, but if you like challenges they are great. To start, jump up to Betelgeuse, then look for Meissa (39 Lambda Orionis). From Betelgeuse travel ¾ of the distance to Meissa and on that line you will find the planetary nebula NGC 2022. This planetary is very small and round with no central star visible. I found it without a filter but I had to flash it with a filter to confirm that I had it in the scope. (To flash an object, move an OIII filter in between your eye and the eyepiece while observing a suspected nebula. If it is a nebula it will stay bright while the rest of the field will dim.)
From NGC 2022 return to Betelgeuse and travel up Orion's arm to 61 Mu Orionis. From this star move ¾° north then just a touch to the east for the location of NGC 2141. I was unable to locate this one in December but it is there and very faint at magnitude 9.4. Continue up the arm to 70 Xi Oriois; on the map below this is the point where the club starts. With Xi in your finder you will see two small stars just under 1° to the southwest. This is the open cluster NGC 2169. This one is pretty bright and divided into two sections. As you look at this one, it looks like the number "37" written in stars. For the last object this month return to Xi Orionis then move 1½° southeast and you should see the two stars 73 and 74 Orionis in the southeast section of your finder. Sweep your scope slowly towards the south and you will find NGC 2194. This cluster is faint at magnitude 8.5 but it is really a rich cluster with the stars all at about the same magnitude.
I have had a lot of fun finding information on Orion and looking for the deep sky objects in it this month, I hope you get a chance to check out at least the bright ones. I can't think of a more impressive constellation to start out the year 2000.
Happy Star Hopping...Eric
Copyrighted © 2000 by Stockton Astronomical Society
Lasted Updated: 12/2/2000
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