Orion the Hunter
Orion is one of the most easily identifiable constellations in the sky. The three stars on Orion’s belt, as well as the four (limbs) enshrouding them, seem to leap out at you once you know what to look for. His shoulder is marked by the red supergiant Betelgeuse (literally “armpit of the central one” in Arabic), and his left leg is marked by the blue-white supergiant Rigel.
But do you see that little pink blob just below the belt? That’s no star at all, that’s the Orion Nebula, one of the only nebulae in the whole sky visible to the naked eye. Even through a small telescope, it’s a beauty to behold.
For the Observer
Alpha Orionis, Betelguese (05h52.5m +07° 24’)means “the armpit of the giant. It is a huge swollen red supergiant 650 light years distant. The star is a class M2 of magnitude 0.8, and it expands and contracts by 20 % of its diameter. These variations are actually quite spectacular and the diameter ranges from between 700 and 1000 times that of our Sun! Betelguese has a surface temperature of about 3400 K. Because massive stars burn their fuel at a much faster rate, Betelguese has an estimated lifetime of only 5 to 10 million years (as opposed to our Sun’s lifetime of 10 billion years.) Bigger is not always better!
Beta Orionis, Rigel (05h15m -08 12’) the “left foot of Orion” is a 0.1 magnitude class B8 blue supergiant about 800 light years distant. Rigel’s luminosity is about 55,000 times greater than our Sun. If Rigel was as close as Sirius, it would appear as bright as a crescent moon! Rigel has a 6.7 magnitude bluish companion that is believed to by a physical binary.
Gamma Orionis, Bellatrix (05h25m +06° 21’) means “female warrior.” Bellatrix is a class B2 blue supergiant with a magnitude of 1.6. The star is 300 light years distant. It is a relatively young star, probably less than 10 million years old. Bellatrix appears to be surrounded by a shell of expanding gas indicating the star is ejecting some of its atmosphere into space.
Delta Orionis, Mintaka (05h32m -00° 18’) means “the belt” which is where this star is located in Orion. Mintaka has a magnitude of 2.2 and is a blue giant class B0 star. Its distance is 800 light years away. Mintaka is both a visusl and spectroscopic binary. The spectroscopic companion is a blue star, the visual companion is 52 arcseconds from Mintaka. There is a bluish 6.7 magnitude companion to Mintaka. The stars form a physical pair with a separation of about 0.5 light years.
Kappa Orionis, Saiph (05h48m -09° 40’) is a 2.1 magnitude class B0.5 blue supergiant. The star is 2,000 light years distant.
M42 (NGC 1976) The “Great Nebula in Orion.”(05h32.9m -05° 25) This beautiful gaseous nebula can be found in the sword of Orion, and can be seen is a pair of binoculars. In telescopes, it is breathtaking! This glowing cloud shines by the light of stars embedded within. M42 is a stellar nursery, where star formation is taking place. The nebula is about 1600 light years distant and about 30 light years accross.
M43 (NGC1982) (05h33.1m -05° 18’) This is actually a detached portion of the Great Nebula M42. It has a bright class O bluish central star.
NGC2194 (06h11m +12° 50’) Cluster of about 100 stars with an overall magnitude of about 9.
NGC2169 (06h05.7m +13° 58’) Small compact cluster. Overall magnitude of 8.
Orion is the legendary great hunter of the Greek mythology. It was said he was the most beautiful of men and the most skillfull of hunters. Unfortunately Orion accepted this praise with utter confidence it was true, and then some. He began boasting of his skills, claiming to have total superiouity over all creatures. Quite naturally, this annoyed the gods that be and they decided to punish him for his greatly inflated ego. Firmly believing in capitol punishment, the gods sent Scorpius, the scorpion was to earth to sting Orion’s foot, and kill him. Diana, an admirer of Orion (and his ego) implored the gods to place the great hunter in the sky to remember him by. This they agreed to, so long as they also placed the scorpion there to warn against such nasty crimes as ego. In Orion’s last dying breatls he begged not to be placed near the scorpion. And so, Orion dominates the winter skies while Scorpius’ domain is the summer skies.
Sources: 1, 2, 3 Top image credit: Jim Delillo