Movement & change
It will take a while, but Orion’s stars are on borrowed time
Everything is in motion all around us. The molecules of gas in the atmosphere swirl and mix daily, the planet itself is hurtling through space as it orbits the sun, even the ground under our feet is moving. Everything changes. It’s just a matter of time and attention to see that this is true. Stability, consistency and permanence are all an illusion.
I am 45 years old. This means that Earth has managed to orbit the sun 45 times while I have been alive. It takes about 27 days for the moon to orbit Earth, which it has accomplished about 608 times since my birth. This may seem like a lot, but it’s all a matter of perspective. Jupiter, which lies about five times farther from the sun than Earth, has only managed to orbit the sun about four times in my 45 years. Saturn hasn’t even made two full orbits in that time.
Even the sun, the center of our solar system, is in motion. We are a part of a massive collection of other stars that swirl in a giant spiral around a galactic core. This group of stars has been named the Milky Way galaxy and it, too, is in motion. The spiral makes one full turn every 230 million years and it is moving relative to the other galaxies in ways so complex that they are indescribable without powerful computers.
The great comfort in all of this is that our human lives are so short that we see the heavens moving in such super slow motion that we can say the stars themselves appear to be in fixed positions. Our grandparents saw the same sky as we see and our children will continue to see the same sky that we have observed.
For as long as humans have been able to think, they have looked into the nighttime sky and seen patterns. Today we call them constellations, but in the past they have been seen as gods, ghosts and other supernatural beings. The most recognizable of them all is probably the Big Dipper, which rotates around the North Star. But if you look to the south, particularly at this time of year, you can see the second most recognizable constellation — Orion — marching across the sky.
The culture in which you were raised will determine exactly what pattern is played out when you look at Orion. Some see a man kneeling behind a shield, while others see a hunter holding a club in one hand and the body of a lion in the other. But the general consensus is that Orion is a hunter of some kind. Whatever you see, there are a few stars that serve as the basic core of the constellation. The most obvious of these are two groups of bright stars that occur in lines of three.
Since I have been getting up in the dark to get to school on time, I have been looking at Orion for a long time and have wondered just what kind of stars these are. I have many books and access to the Internet to help me look these things up. I even have an app on my iPad that will help me find the constellations. I am not the first person to be curious about these things, but it is interesting to lay out what we know.
Orion’s right shoulder is marked by the star Betelgeuse, which is a massive red supergiant that lies 641 light years from Earth. If Betelgeuse were at the center of our solar system, its edges would extend out past Mars. It is incredibly large, but the cost of being this size is a short life. Our sun is expected to live about 9 billion years, but Betelgeuse will be lucky to see 15 million years. Upon its “death,” the star will explode into a supernova that will be visible during the day here on Earth. But none of us will see it.
Betelgeuse is a rogue star that lives fast and dies young. It has broken away from the stellar nursery in which it was born.
Moving clockwise, we come to the star known as Meissa, another supergiant, but this time a blue supergiant. As seems to be the case with the stars in Orion, Meissa is another rogue star that has lost some mass and picked up speed. What we can’t see with the naked eye is the fact that Meissa is actually more than one star, but at just over 1,000 light years away you can’t really see this with the naked eye. Like Betelgeuse, Meissa will live a short, bright life. Its name is derived from the Arabic “Al-Maisan,” which means “the shining one.”
Clockwise again we come to Bellatrix and, before I go any farther, the answer to your question is “yes.” The character Bellatrix Lestrange was indeed named after this star, which has also been called the “amazon” and the “female warrior.” It is another blue giant and it is also very young; at least its 20 million years is young when talking about stars. Bellatrix is also rather close to Earth. Had George Washington headed into the heavens at light speed, instead of crossing the Delaware in a boat, he would have reached Bellatrix by now.
Moving clockwise again, we come to the star Mintaka. This star is on the right-hand side of Orion’s “belt” and its name is derived form the Arabic word “mantaqa,” which means “belt.” Another double star, Mintaka is actually a giant star and a smaller sun-like star that spin around one another every six days. Each one of these stars is about 90 thousand times brighter than the sun, which is why they are so easily seen from 700 light years away.
Clockwise again we come to what may be the most famous star in Orion, Rigel. Anyone who has been a fan of science fiction will recognize this name. Star Trek talked about Rigel from time to time, Battlestar Galactica had a Rigel character, and there was a short-lived sci-fi series called Far-Scape that featured a character called Rigel. This is the brightest star in the constellation, but once again it is not a single star. Rigel is in fact a triple star, dominated by another blue supergiant.
Moving clockwise to Orion’s left “knee” we come to Saiph. Once again we are looking at a supergiant about 700 light years from Earth, which puts it about the same distance from us as Rigel. This star is “burning” at a temperature much hotter than that of Rigel, but because it emits so much of its energy in the form of ultraviolet light, it appears much dimmer to our eyes. Birds, which can see in the UV spectrum, might see it as a shining beacon during their nighttime migrations.
Another move clockwise and we move up to the left-hand star in Orion’s belt, Alnitak. Once again we are looking at a blue supergiant and the name is of Arabic origin where the word “an-nitaq,” means “girdle.” However, it is interesting to note that the stars of Orion’s belt have been named by many cultures around the world. Orion’s position in the sky means that it is visible to everyone at some time of the year. Scandinavian peoples saw a distaff, which is a tool used for spinning wool into thread. The native people of Mexico saw three animals (the mule deer, the pronghorn, and the bighorn sheep), which were pursued by the hunter.
The central star in Orion’s belt is called Alnilam. Guess what kind of star it is? If you said it’s a blue supergiant, you’ve been paying attention. It’s another massive, short-lived star that is probably going to explode in the next million years or so, but humans may not even exist at that point.
Extending down in a linear arrangement from Alnilam is a series of three stars that are sometimes called Orion’s sword. This is another binary star, but this time the two stars are visibly separate — even in my photo. Dominated by yet another supergiant, this system is 2,330 light years from Earth, which suggests that it is not related in any way to many of the other stars in the constellation.
If you find yourself awake in the early morning hours of winter, take a moment to look up and to the south. Orion is there, hunting in the dark and he may help you feel like you’re not quite so alone as you might feel.
Bill Danielson has worked as a naturalist for 16 years. In that time, he has been a national park ranger, a wildlife biologist and a field researcher. He currently works as a high school chemistry and biology teacher. His Speaking of Nature column runs weekly in The Recorder, except for the first Thursday of each month, which is when his Kids and Critters column for young readers appears. To contact Bill, or to learn more about his writing, visit www.speakingofnature.com