Orion (IPA: /ə(ʊ)ˈrʌɪən/), a constellation often referred to as The Hunter, is a prominent constellation, perhaps the best-known and most conspicuous in the sky. Its brilliant stars are found on the celestial equator and are visible throughout the world, making this constellation universally recognized. In the northern hemisphere Orion is visible in the evening from November to April
According to the most common contemporary imagery: Orion is standing next to the river Eridanus with his two hunting dogs Canis Major and Canis Minor, fighting Taurus the bull. Other prey of his, such as Lepus the hare, can be found nearby.
There are other contemporary names for Orion. In Australia, the belt and sword of Orion are sometimes called the Saucepan, because the stars of Orion's belt and sword resemble this kitchen utensil as seen from the southern hemisphere. Orion's Belt is called "The Three Kings" (or "The Magi") in some places. The constellation is also known as an "Amber" in other commonwealth countries such as the United Kingdom. Historically it has had other names, perhaps the earliest known is the Babylonian "Shepherd of Anu ", corresponding to an apparent representation of the constellation Auriga or an element of it, as a shepherd's crook.
- λ Ori (Meissa) is Orion's head.
- α Ori (Betelgeuse), at its right shoulder, is a red star with a diameter possibly larger than the orbit of Mars. Although it is the α-star, it is somewhat fainter than Rigel. Betelgeuse is actually a sextuple star (other studies say it has only two companions, and the existence of any companion at all is disputed), but its companions are too small to be easily seen. It forms a point of the Winter Triangle.
- γ Ori (Bellatrix), "warrior woman", is at Orion's left shoulder.
- ζ Ori (Alnitak), ε Ori (Alnilam) and δ Ori (Mintaka) make up the asterism known as Orion's Belt: three bright stars in a row; even from these alone one can recognize Orion.
- η Ori (Eta Orionis), between Delta Orionis and Rigel.
- κ Ori (Saiph) is at Orion's right knee.
- β Ori (Rigel), at the constellation's left knee, is a large blue-white star, among the brightest in the sky. It has three companions, also difficult to see.
- ι Ori (Hatsya) is at the tip of Orion's sword.
The major stars of Orion are all very similar in age and physical characteristics, suggesting that they may have a common origin. Betelgeuse is the single exception to this.
Orion is very useful in locating other stars. By extending the line of the Belt southeastward, Sirius (α CMa) can be found; northwestward, Aldebaran (α Tau). A line eastward across the two shoulders indicates the direction of Procyon (α CMi). A line from Rigel through Betelgeuse points to Castor and Pollux (α Gem and β Gem). Additionally, Betelgeuse forms part of the Winter Triangle, and Rigel is part of the Winter Circle. Sirius and Procyon, which may be located from Orion by tracing lines, also are points in both the Triangle and the Circle.
See also the list of stars in Orion.
Notable deep sky objects
Hanging from Orion's belt is his sword, consisting of the multiple stars θ1 and θ2 Orionis, called Trapezium and the nearby Orion Nebula (M42). This is a spectacular object which can be clearly identified with the naked eye as something other than a star; using a pair of binoculars, its swirling clouds of nascent stars, luminous gas, and dust can be observed.
All of these nebulae are part of the larger Orion Molecular Cloud Complex which is located approximately 1,500 light-years away and is hundreds of light-years across. It is one of the most intense regions of stellar formation visible in our galaxy.
The configurations of the constellation Orion roughly formed about 1.5 million years ago, because of relative slow movements of stars within the constellation from earth's perspective (especially the belt of Orion), constellation Orion will remain visible in the night sky for the next 1 to 2 million years, making the constellation one of the longest observable constellation parallel to the rise of human civilization. (result generated from SkyChart III).
Being so bright and distinctive, the pattern of stars that form Orion were recognized as a coherent constellation by many ancient civilizations, though with different representations and mythologies.
The ancient Sumerians saw this star pattern as forming part of an image of a shepherd (sometimes in a chariot) with his sheep and in some versions a shepherd's crook, while in ancient China, Orion was one of the 28 zodiac signs Xiu (宿). Known as Shen (參), literally meaning "three", it is believed to be named so for the three stars located in Orion's belt. (See Chinese constellation)
The stars were associated with Osiris, the god of death and underworld, by the ancient Egyptians. The Giza pyramid complex, which consists of the Great Pyramid of Giza, the Pyramid of Khafre and the Pyramid of Menkaure, is said to be a sky-map of the Belt of Orion, that is, of Osiris.
References in ancient Middle Eastern and Mediterranean literature to the "belt and sword" imagery of Orion are those most often echoed in modern western literature and for this reason this imagery has found its way into popular western culture, for example in the form of the shoulder insignia of the 27th Infantry Division of the United States Army during both World Wars, probably owing to a pun on the name of the division's first commander Major General John F. O'Ryan.
Around October 21 each year the famous Orionid meteor shower reaches its peak. Coming from the border to the constellation Gemini as much as 20 meteors per hour can be seen. More information about this meteor shower and the Chi Orionids, which are active around the beginning of December can be found in the meteor shower calendar by Gary Kronk.
- Map of Orion
- The Deep Photographic Guide to the Constellations: Orion
- Anne Wright's page on Orion Note: Astrological perspective
- Melbourne Planetarium: Orion Sky Tour
- The clickable Orion
- WIKISKY.ORG: Orion constellation