2011 Constellation Guide: Orion

Orion

• Symbolism: Orion, the Hunter
• Main Stars: 7

Position in the Sky

• Right Ascension: 5 hours
• Declination: 5 degrees
• Visible between latitudes 85 and -75 degrees
• Best seen in January (at 9:00 PM)

Named Stars

• Betelgeuse (Alpha Ori)
• Rigel (Beta Ori)
• Bellatrix (Gamma Ori)
• Mintaka (Delta Ori)
• Alnilam (Epsilon Ori)
• Alnitak (Zeta Ori)
• Saiph(Kappa Ori)

Messier Objects

• M42 The Great Orion Nebula (diffuse nebula)
• M43 part of the Orion Nebula, de Mairan's Nebula (diffuse nebula)
• M78 (diffuse nebula)

Meteor Showers

• Orionids
• Around October 21st annually , the Orionid meteor shower reaches its peak. The meteors originate from Orion's border with Gemini. The zenithal hourly rate is about 20.
• Chi Orionids
• Peaks around December 2nd with a ZHR of about 3.

Mythology

The Greek poet Hesiod says that Orion was the son of Euryale, the daughter of Minos, and of Poseidon, and that there was given him as a gift the power of walking upon the waves as though upon land. When he was come to Chios, he outraged Merope, the daughter of Oenopion, being drunken; but Oenopion when he learned of it was greatly vexed at the outrage and blinded him and cast him out of the country. Then he came to Lemnos as a beggar and there met Hephaestus who took pity on him and gave him Cedalion his own servant to guide him. So Orion took Cedalion upon his shoulders and used to carry him about while he pointed out the roads. Then he came to the east and appears to have met Helius (the Sun) and to have been healed, and so returned back again to Oenopion to punish him; but Oenopion was hidden away by his people underground. Being disappointed, then, in his search for the king, Orion went away to Crete and spent his time hunting in company with Artemis and Leto. It seems that he threatened to kill every beast there was on earth; whereupon, in her anger, Earth sent up against him a scorpion of very great size by which he was stung and so perished. After this Zeus, at one prayer of Artemis and Leto, put him among the stars, because of his manliness, and the scorpion also as a memorial of him and of what had occurred.

Features

Orion is one of the most recognizable constellations in the sky, home to some of the brightest stars, and a few deep-sky objects, most notably the Orion Nebula.  You can easily locate Orion by looking southward to his right shoulder; Betelgeuse, a variable red supergiant, averaging around the 9th brightest star in the sky, and the 2nd  brightest in the constellation.  Going west to his left shoulder is Bellatrix, the 3rd brightest star in Orion.  Bellatrix is the 27th brightest star in the sky.  It is also known as the Amazon Star. It was once thought to belong to the same group as the stars of Orion’s belt; Alnitak, Alnilam, and Mintaka, but this is no longer believed to be the case.  Looking southwest to the left foot is Rigel, the brightest star in the constellation and the 6th  brightest in the sky.  Across to the east you’ll find the right foot; Saiph. The name is from the Arabic saif al jabbar; sword of the giant.
Crossing Orion’s waist from east to west is Alnitak, Alnihim and Mintaka; together this group creates Orion’s Belt.  These stars may also be named the Three Kings or the Three Marys.  They also mark the northern night sky when the sun is at its lowest point, and were a clear marker for ancient timekeeping.  Hanging from Orion’s Belt is his sword; containing the breathtaking Orion Nebula. This is one of the brightest nebulae in the sky, and can be viewed by the unaided eye. It is also an active star forming region; new stars are currently being born there. The most notable feature of the Orion Nebula is the Trapezium. This is a tight open cluster of stars right in the center of the nebula. If you can resolve the 5 major stars of this cluster, you have very good seeing.
The Horsehead Nebula is located just south of Alnitak. It is a dark nebula; a cloud so dense that it blocks the light behind it. The nebula was given its name due to the shape that the swirling gas and dust form; it looks like a horses head! The red glow comes from the hydrogen gas reflecting the light from the nearby star Sigma Orionis. There are also new stars forming in this nebula.

Looking south to Orion.  Orion and Horsehead Nebula enlarged.