On a clear and dark mid-winter night, the most-striking thing up there in the sky is the constellation of Orion. It is easily the best-known star grouping in the heavens, and since it is straddling the celestial equator, there is no place on earth where it is not visible. With its bright, colorful stars, it is hard to overlook.
Early on a February evening it will be standing more or less upright in the south. If you are not familiar with Orion, look for a large rectangle with two bright stars diagonally opposite from one another. Look closer for the color difference between the two. At the lower right, bright-white Rigel is the brightest in the constellation and one of the brightest stars in the sky. It is a youthful star only a few million years old and bursting with energy. It is burning with the brightness of at least 60,000 of our suns and probably a lot more. Astronomers call it a blue-white super giant and say it will blow its guts out as a supernova explosion in another million years or so.
In the upper left-hand corner of Orion, the orange-reddish looking star is Betelgeuse, a strange name for a strange star. The name dates back thousands of years and its exact meaning is somewhat murky in the depths of antiquity. It probably means shoulder of the giant or even armpit of the giant, but also could be translated as the armpit of the sheep wearing the white girdle. Whatever it means it is a weird name for a star.
Having swelled up in its old age, it is probably the largest star we can easily see in the sky. If it were the size of a huge red beach ball as tall as a 10-story building, then our earth would be the size of the period at the end of this sentence. Betelgeuse will end its life in a supernova explosion also, but much sooner than Rigel. Put that event on your calendar for just a few tens of thousands of years from now.
The most obvious part of Orion is his belt, three equally bright stars, evenly spaced, almost in a straight line. There is nothing else in the sky quite like it. All three of them are young super-bright and hot stars just a few million years old. They are so bright and so far away that nobody knows how bright or how far away they actually are. The one in the middle, Alnilam is its name, might possibly be the brightest star we can see with the naked eye. It could be shining as much as 800,000 times the brightness of our sun. What would it be like if our own little earth were circling a star like that? Well, you would get a lethal sunburn in just seconds, so stock up on plenty of sunscreen. Our earth would have to be much farther away from Rigel to avoid being scorched, about 10 or 20 times farther away than Pluto is from our sun.
Orion and the pyramids
Some scholars think that the three large pyramids at Giza are actually lined up with the three stars in Orion’s Belt. They claim that mysterious shafts buried deep in the edifices point to the constellation of Orion. Supposedly the Egyptian gods Isis and Osiris came from Orion. All this is highly controversial, so do not get too attached to the idea, but there is something intriguing about it.
Line up those three belt stars and point down and to the left to the bright star Sirius, the brightest star in the sky. Remember when we look up at the dome of the heavens, we see it in two dimensions only. Is Sirius bright because it is close to us, or is it a really bright star? In this case it is close, and not very bright, only 25 times as bright as our sun.
That parade of planets in the southwestern sky at dusk has mostly marched off into the sunset glow. Only Jupiter is left, a bright, non-twinkling light low in the southwest just after sunset. Look for Venus before dawn in the east just above where the sun will rise.
When you are standing out there in all that snow, and your feet are freezing, try to wrap your head around the idea that you are looking at those stars in Orion that are not only far away, but also far back in time. Sirius is only eight-and-a-half light years away, which means that the light you are looking at started its journey to your eyes eight and a half years ago. That is not to hard to grasp, it is in your lifetime. The light from Rigel and Betelgeuse has been traveling hundreds of years to reach you, and the light from the belt stars set out over a thousand years ago. Stargazing is an activity where you can literally travel back in time!