Orion, the constellation
Published on Jan 10, 2006 at 7:44 pm.
1 Comment.
Filed under constellations.
A while back, I did a blog entry on the Orion spacecraft program. Now, I figured that I’d say a few things about the constellation itself. Todd Lean has a nice web page showing a very good photograph of Orion, with star designations.
Orion is portrayed as a great hunter. You can see Orion in the East after sunset, by about 10pm it is high in the southern sky, and it sets a bit before dawn. Orion is an ancient constellation, and is even mentioned in the Bible in the book of Job, as well as in Amos.
Orion is one of the most easily recognized constellations because of the three stars across his middle that represent his belt. These stars, in order from left to right, are Alnitak, Alnilam, and Mintaka. Collectively, these three stars are called Alnijad (meaning “belt”) or Alnasak (meaning “line”). These are all Arabic names, as you might can tell.
The brightest star in Orion is Rigel, located in the lower right corner of the stick figure that we often use to portray the constellation. Rigel is a monster star that is very bright. It is one of the most distant stars that you can see in the sky, but it is still one of the dozen brightest. Rigel means “foot”, and represents the foot of Orion. However, since Rigel means foot, there are more Rigels in the sky than just this one! Most any of the constellations that have a bright star near where the foot is normally supposed to be have that star named Rigel. However, only two of these stars are very bright, so it is generally assumed that you mean one of those two if you talk about the star named Rigel. The other one is in Centaurus, and we often designate it Rigel Kentaurus, or just Rigel Kent, to differentiate it from the Rigel of Orion. To further remove confusion, Rigel Kent is normally referred to by its Bayer designation of Alpha Centauri.
The star in Orion’s upper left quadrant is called Betelgeuse, which means “armpit.” Don’t blame me! I didn’t name these things! Betelgeuse is a red supergiant star. If you were to set it where the Sun is, the outer surface of the star would be from the center of the star nearly five times the distance between the Sun and the Earth! Everything inside the orbit of Jupiter in our solar system would be inside Betelgeuse! Despite its great size, Betelgeuse only has a mass dozens of times the mass of the Sun, so it is very thin and tenuous. It is also a variable star, and it pulsates somewhat, but in an irregular fashion.
Coming down from the belt is a line of dim stars that we refer to as Orion’s sword. Near the bottom of the sword you can see (with good eyes and dark skies) a faint fuzzy patch. It is obvious in binoculars, and beautiful in a telescope. This fuzzy patch is called the Orion Nebula. It is number 42 on Charles Messier’s list of fuzzy things that are not comets. I have often wondered how such an obvious thing got to be so far down on the list. There are some indications that it is currently brighter than it was a couple hundred years ago, but not by so much, I’d think. The Orion Nebula is a region of gas and dust (about 90% hydrogen by number of atoms, and just under 10% helium, with just under 1% other stuff). This gas and dust is collapsing to form new stars. In fact, the Hubble Telescope has shown several solar systems in this nebula that are in the process of forming. The first stars that form out of such a nebula are the biggest, brightest, and hottest stars, which produce a huge amount of ultraviolet light. The UV light then can ionize the gas in the vicinity of these stars. As electrons recombine with the protons to form neutral hydrogen again, then the hydrogen emits light. Much of this light is reddish, so color photographs of the Orion Nebula often show pretty red and pink colors. Don’t expect to see the color in a small telescope though. The cones in your eye (the color receptors) need a minimum intensity to fire, but the rods (black and white) detect light at far lower intensities. So, unless you are looking through a VERY large telescope, you’ll see the nebula in black and white. However, even rather small amateur telescopes can be used with cameras taking time exposures to produce these colors. To illustrate how big and bright the nebula is, just think that you are seeing it with the naked eye (dark skies) from over 1500 lightyears away!
pI could keep going on about Orion, but I don’t want to bore y’all. I figured, though, that I’d say one more thing. Orion the hunter comes to us from Greek and Roman traditions. Obviously this constellation is prominent in the night sky, so other people have seen it and thought of it as something other than a hunter. For example, the MesoAmerican people thought of it as two triangular cooking hearths with a woman standing between them. The nebula made a fuzzy patch in the middle of one of the hearths, so that was a loaf of bread cooking. I am having trouble attaching an illustration of this, but I might add one tomorrow.
-Astroprof
Pink Cameras on August 21, 2008 at 1:57 am: 1
I wonder- The Orion’s upper left quadrant is called Betelgeuse. And what can be said about the distance between the Sun and the Earth !!! Really good matter to have search upon. The Orion Nebula is a region of gas and dust. But why this region is so concentrated? thinking if ever it enlarge with greater speed…….!
I say thanks to Ozone layer which protect from such UV rays, but to man unconscious or self-fish state of nature soon many more problems can arise. Yes, its matter to think….!