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.

DSOs On A Clear Spring Evening

I managed to step outside for a while the Saturday night - which happened to be one of the clearest nights we've had this spring. Although the warmer nights are more enjoyable, the clouds that have been forming in the evening are less than desirable.

I've kinda been on a cluster streak lately and I was in the mood to see a new galaxy or nebula. I began with M3. This cluster is one of the largest and brightest, oldest and is made up of around 500,000 stars. I can tell that this would be a beautiful dense cluster in a larger scope, but with my 8" and my skies it was mostly dim and washed out. I could make out the texture and individual stars - it just wasn't very sharp.

Next up was M63, the Sunflower Galaxy, then M51. M63 was just a gray smudge with a bright core, and M51 had eluded me in the past (poor seeing) so I was happy to finally catch it on this clear night. As faint as it was, I was actually able to tell it was spiraled. Darker skies and more aperture will bring out the spiral structure and core in this galaxy. I then spotted M101 and M109 - M101 being the absolute faintest object of the night. I was only able to detect it after about a minute of staring and using averted vision - it was like trying to see a ghost. M108 was actually more distinguishable than M63, but still very faint.

After moving away from M108, I changed my mind and decided to go back for another look. I'm really starting to dislike my [6x30 no cross-hair] finder scope, and finding my way back just wasn't as easy as it could be. While searching for 108 again, I found another object which surprised and thrilled me. It wasn't on the map I had with me, so I had no idea what I was looking at, but it was a very large round cloud. I eventually realized that I could put this object and M108 in the same FOV, which was beautiful and exciting. After I got back inside and had a chance to look it up, I found out I had spotted the Owl Nebula (Messier 97). How very cool! All in all, very satisfying for me. The best find though was M81 and 82 (Bode's Nebula/Galaxy) side by side. These were the most distinct objects I found, and were a great pleasure to see. Everything I saw was best viewed at 48x with my 25mm Plossl. I have a Barlow coming in this week, and am looking forward to using it. 150x was just too much for the galaxies except for M51 and 63.