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Orion (constellation)

Orion

larger image
AbbreviationOri
GenitiveOrionis
Meaning in Englishthe Great Hunter
Right ascension5 h
Declination
Visible to latitudeBetween 85° and -75°
On meridian9 p.m., January 25
Area
 - Total
Ranked 26th
594 sq. deg.
Number of stars with
apparent magnitude < 3
6
Brightest star
 - Apparent magnitude
Rigel (β Orionis)
0.12
Meteor showers
Bordering constellations

Orion, the Hunter, is a prominent constellation, perhaps the best-known in the sky. Its brilliant stars, on the celestial equator and visible throughout the world, make this constellation universally recognized.

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 like Lepus the hare, is also nearby.

Table of contents

Notable features

The constellation is extremely rich in bright stars and in deep-sky objects. Here are some of its stars:

  • Heka is Orion's head.
  • Betelgeuse (α), at its right shoulder, is a red star[?], larger than the orbit of Venus. This is actually a sextuple star, but its companions are too small to be easily seen. Betelgeuse forms a point of the Winter Triangle.
  • Bellatrix[?] (γ), "warrior woman," is at Orion's left shoulder.
  • Alnitak[?], Mintaka[?] and Alnilam[?] (ζ, δ and ε) make up the asterism known as Orion's Belt: three bright stars in a row; even from these alone one can recognize Orion.
  • Saiph is at Orion's right knee.
  • Rigel (β), at the constellation's left knee, is a large white star, among the brightest of the sky. It has three companions, also difficult to see.

The major stars of Orion are all very similar in age and physical characteristics, suggesting that they may have a common origin. Betelgeuse is an exception to this, however.

Orion is very useful in finding other stars. By extending the line of the Belt southwestward, Sirius (α Canis Majoris) can be found; northeastward, Aldebaran, α Tauri. A line eastward across the two shoulders indicates the direction of Procyon, α Canis Minoris. A line from Rigel through Betelgeuse points to Castor and Pollux, α and β Geminorum.

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 that can clearly seen not to be a star with the naked eye; in binoculars, its swirling clouds of young stars, luminous gas, and dust can be seen.

Another famous nebula is IC 434, the Horsehead Nebula[?], near ζ Orionis. It contains a dark dust cloud whose shape gives the nebula its name.

Besides these nebulae, surveying Orion with a small telescope will reveal a wealth of interesting deep-sky objects.

History

Being such a brillant pattern of stars, Orion is recognized by many ancient civilizations, though with different images.

The ancient Sumerians saw this star pattern as a sheep. The name Betelgeuse literally means "the armpit"; in case of the Sumerians it meant "the armpit of the sheep".

In ancient China, Orion is one of the 28 zodiac Xiu (宿). Known as Shen (參), literally meaning "three", it is probably named because of the three stars on Orion's belt. See Chinese constellation.

The stars were considered to be a tribute to the god of light, Osiris by the ancient Egyptians.

The "belt and sword" of Orion are frequently referred to in ancient and modern literature, and even found recognition as the shoulder insignia of the 27th division of the United States Army during both World Wars, probably due to the fact that the division was commanded by General O'Ryan.

Mythology

It is not very surprising to see such a prominent constellation to have more than one version of story around it in Greek mythology. In one version, Orion claims himself to be the greatest hunter in the world. This is heard by Hera, the wife of Zeus, and she decided to send a scorpion. after Orion. Orion is stung to death by the scorpion. Zeus felt sorry for Orion and put him onto the sky. The scorpion is also taken up to the sky, becoming the constellation Scorpius. It is an interesting fact that when one of the two constellations rises from the horizon, the other would have already set. So the two rival can never see each other again.

See also Orion (mythology).

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