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Orion - Myth and Science - Part 2
Observing > The last time we were together we learned how the great constellation of Orion was not exclusively a European constellation by any means. Peoples on every continent have thrown their own stories and characters up there into that conspicuous part of the sky.
Now we hit the scientific stories, our best insights into what precisely those points of light and fuzzy clouds really are.
Let's start with Betelgeuse, the reddish-orange star that makes up one of the bright corners of the quadrangle, specifically the star in the upper left.
The name Betelgeuse is possibly derived from the Arabic for "armpit of the central one." Some think it might have come from the Arabic for "shoulder" or "hand," but those interpretations don't cause nearly as many snickers.
What we do know is that Betelgeuse is one enormous star, yes-sirree-bob. It is in its red giant stage, the final act in The Life of an Enormous Star. When a star begins to run out of fuel it goes through some crazy death throes, one of which is to expand. Betelgeuse has expanded so much that if we could put it where our own Sun is, it would swallow up all the planets out to Jupiter. That is one big star.
We're happy it's over 400 light years away, because when it finally self-destructs as a supernova in just the next thousands of years, it will spew lethal radiation for hundreds of light years around it, sterilizing the vicinity. Are we completely safe? We don't know yet.
On the opposite corner of Orion's hourglass figure is Rigel, the "foot" of the Great Hunter. It is the brightest star in Orion, and one of the brightest stars in the galaxy. To be over 775 light years away and still burn that brightly means Rigel is one energy-gushing star.
In fact, bluish-white Rigel is over 90 times bigger than our sun and pours out more than 50,000 times more energy.
From left to right, Alnitak, Alnilam, and Mintaka make up a triplet of other fiery, fast-burning stars, those that make up Orion's Belt.
They are about the same type and size of star as Rigel, telling astronomers that perhaps Rigel and the Belt Stars - and some of the other stars of the Hunter - were formed in the same super colossal stellar womb, the same cyclopean cloud of gas and dust, some ten million years ago.
We can see residual star formation still going on in the most famous nebula in the sky, the aptly named Orion Nebula.
Just below the Belt, and visible to the naked eye, is this cloudy-looking area of intense star birth. A decent telescope will bring out the four brightest stars in the heart of the nebula - the Trapezium. But the whole immense gas cloud is lit up from the energy of just one of those stars.
Theta1 C Orionis - yes, that's its real name - is that crybaby toddler star, the brightest of the four. It screams out so much nasty radiation, specifically ultraviolet, that it energizes the cloud to the point of lighting it up like a lightyears-across neon sign.
It has just millions of years left before it, too, detonates as a supernova.
The whole of Orion is an example of the fleeting nature of constellations. Often they are made of bright, massive stars that live fast and die young. Orion wasn't in the sky when dinosaurs ruled the earth. He won't be there in about 10 million years, by which time the major stars of the Great Hunter will have long since reached their expiration dates.
Like the Orion of mythology, this constellation is destined for a life cut short. Enjoy it while you can.
Posted by Mark Ritter at 2007.01. 7 06:42 PM | Comments (0)
