Sunday, September 16, 2012

A Sirius Discussion of Orion

A recent photograph of the night sky posted by my nephew Jacob contained an excellent view of the constellation Orion and, at his heels like a good hunting dog, Sirius the Dog Star. That got me thinking about my past. I’ve always had a deep interest in Astronomy, and I own several astronomical telescopes. This meshed with another discussion I had recently regarding mid-life (or maybe in my case more “late-life”) crisis. I contended that the so-called “mid-life crisis” occurred when an individual first realized that they were not going to accomplish the goals that they had held since adolescence. Since my goal from about the age of eight was to be a scientist, and since I think I accomplished that goal, therefore, using modus ponens, I am incapable of having a mid-life or late-life crisis.

Now as you gentle readers know, I usually describe myself as an engineer, but that is certainly a scientific title, even if it is more on the practical application side of the spectrum. In fact, at one point in my IBM career, my official title was “engineer/scientist.” On the other hand, my current official title is “senior technical staff member.” Try to figure out what you are from that title! But let’s go back, back, back …

My earliest recollections were when I was about eight years old. I knew then I wanted to be a scientist. My first love was astronomy. That sprinkled with a little physics. (I was intrigued by aspects of Einstein’s theory relative to traveling faster than the speed of light. I’ll discuss that little episode in some other note. It was natural, however, to associate that speed of light with astronomy since the distance to the stars is often measure in the distance light can travel in one year, a “light year.”)

The clear skies of Montana were very conducive to a young observer, and I collected astronomy texts from the library and started to learn the names of stars and constellations, which are collections of stars that appear to form patterns.

In 1956, at the age of nine, I was somewhat sidetracked when Doctor Arthur Howard from Stanford University spent the summer at my parent’s motel doing geological research in the central Montana mountains. He and I spent many lazy afternoons walking the nearby hills and looking at rocks. He later sent me a geology text book. I think that may have been my first book, as up to then I had only borrowed books from the library. (I still have the book and the price is written on the back cover, $4.95, for this Guide to Practical Geology copyright 1955. Just ask Joel or Mark how much college texts have gone up in the 55 years since then.)

Geology did fit with my mother’s deep interest in archeology, and I followed that path for a very short time before becoming interested in electronics and ham radio. That too is a story for another note. I did return to geology somewhat when I graduated from High School and I attended the Montana School of Mines (renamed before I started as “Montana Tech”) for one year, but that was more an act of desperation by a young man who had abandoned his scientific pursuits as he chased wine, women, and song — and not necessarily in that order. I think I went to Montana Tech more to please my dad than to become a geologist.

As you all know, I only spent one year in college at Butte before quiting to spent a few years sowing wild oats in Great Falls, Compton, White Sulphur Springs, and Libby before enlisting in the Navy to study electronics. That led to my career in electronics and teaching and completed with a Bachelor of Science in Electronics Engineering followed by my employment at IBM. One thing followed another and I added math, physics, and computer science to the mix. I had intended to go to Stanford and get a Ph.D., but, again, that’s a story for another time.

I never lost my interest in astronomy, and it was often a favorite discussion topic for me. I remember when I first met our good friends, Steve and Sandi Quintana. At that time they were not married and Steve worked with me at IBM. They came to the house for dinner and I recall taking them out on the back deck and naming all the constellations and stars in the sky. Regardless of that nerdly introduction, Steve and Sandi became our dearest friends.

When I first saw Jacob’s photograph, I was thinking about an upcoming astronomical event, and I recommended to Jacob that he check out the pre-dawn sky on Monday, January 10, for an excellent view of a close planet Venus. In addition, the planet Mercury would also appear quite brightly on that day, although very low on the horizon. Since both Venus and Mercury are closer to the Sun than the Earth, they appear alternating in the morning sky or the evening night sky. At its closest approach to Earth, Venus is only about 40 million miles away. At other times in the year it is clear across on the other side of the Sun and over 200 million miles. So Monday is a good time to view Venus due to its close approach.

I then looked again at his photograph and instantly recognized my old friend, the constellation Orion also known as "The Hunter." It is the most recognizable of all the constellations in my opinion. I always think of it as a giant letter “K.” It contains many fascinating stars and astronomical objects, and is a great subject for discussion … at least I think so. Following right behind Orion, as I mentioned previously, is the brightest star in the sky, Sirius of the constellation Canus Major, the “big dog.” So, naturally, Sirius is called the Dog Star and is a well known companion of Orion.

Let’s talk about Constellations. They are simply patterns of stars that observers for centuries have associated together, sort of like connect the dots, and often have mythological origins and fascinating histories. Orion is usually drawn with a spear or shield held out in front, but the more obvious parts of the constellation represent the two arms and the two legs with a belt across the middle and a sword hanging from the belt.

Let’s start with Orion’s Belt, a series of three, almost identically brilliant stars, in a nice straight, equidistant, line. The belt is an example of an “asterism.”  An asterism is any collection of stars in a simple pattern. Basically an asterism is simpler and smaller than a constellation. Orion’s Belt is the central object of the constellation, and — as I said — is well known for the balance of the three stars. That is their equidistant and straight line appearance as well as the equal apparent brightness.

Now there are two things you should know about stars and constellations in the sky. First is the issue of brightness or as it is technically known, apparent magnitude. Apparent magnitude is a combination of two things: absolute magnitude — how bright the star actually is, and distance from the Earth.

Sirius is a fairly bright star, but there are many, many other stars in the sky that we know have a much higher absolute magnitude. Sirius is about 25 times more luminous than our sun or Sol, but Rigel, a star in Orion, is about 85,000 times brighter than Sol. The primary reason for the apparent brightness of Sirius is its relative closeness to Earth.  It is only about 9 light years away, while Rigel is 700 to 900 light years from Earth. Sirius is actually a star formation. That is it is two (or maybe even three — the jury is still out) stars orbiting around each other. The larger, called Sirius A is white, main sequence star being orbited by a red dwarf. Some researchers think that orbital variations indicate a third star in orbit even smaller than Sirius B.

And what of the stars in the Belt? Well, that is the other thing about constellations. We see them as associated patterns in the sky, but that does not mean they are connected in any way. One star in the constellation may be very close to us while another may be far, far away. The only association is that we see the combination of the light from these bodies in the night sky as stable patterns that rotate through the year as the Earth moves about its orbit around the Sun.

In fact, that is one reason these bodies were so studied by the ancients. They were used to tell time and seasons. The rising of the Dog Star was an indication that the annual floods of the Nile river were about to begin. That and the fact that the ancients had no television are the reasons mankind has looked to the night sky since the very beginning.

The three stars that make up the Belt appear the same brightness and to be in a very precise alignment, yet one is 800 light years from Earth and about 100,000 times more luminous than the sun, and one is nearly twice as far from Earth and about 375,000 times more luminous than the sun. But from our perspective, they all appear about the same. But in reality, there is no connection between these three stars. They just appear in a nice line to our eyes.

In addition to distance and luminance, the stars are all moving in different directions. That means that, in a million years, the constellations will have all changed as the stars move apart. The current configuration of stars now known as the constellation of Orion formed roughly about 1.5 million years ago, as stars move relatively slowly from the perspective of Earth. Orion will remain recognizable in the night sky for the next 1 to 2 million years, making it one of the longest observable constellations, parallel to the rise of human civilization. The Big Dipper, on the other hand, contains stars moving rapidly in relation to our vantage point. In 50,000 years the Dipper will no longer exist as we know it, but be re-formed into a new Dipper facing the opposite way.

Hanging from Orion’s belt is Orion’s Sword made up of several stars and other objects. One of the brighter objects in the sword is not a star at all, but a nebula. Now nebulas are giant clouds of thin gas. (The Orion Nebula is estimated to be 24 light years across.) The cloud is heated up by energy from stars and so it glows. At about 1300 light years away, Orion Nebula is the closest and most studied of all the nebula. I’m sure you will recognize pictures of it. Further, it contains the Horse Head Nebula, another common astrological photograph.

The four stars that make up the arms and legs of the hunter (or the lines of the “K”) are Betelgeuse, a red giant star nearing the end of its life, Rigel, a blue super giant which is the sixth brightest star in the sky, plus Bellatrix and Saiph.

So when you combine the interesting and easily discerned pattern of Orion with its many bright stars and interesting asterisms, it becomes a very noticeable constellation. Add that to the fact it is high in the early evening sky during winter in North America, and I suspect it is a very common experience for viewing.

Jacob said he was looking for the Big Dipper, another asterism which is part of Ursa Major — The Big Bear, and famous for pointing at Polaris, the Pole Star. But he could not find it. I’m sure that in his home state of Alaska, the dipper is very prominent. But I’m not surprised that, in Mississippi, his camera seemed to seek out Orion.

So that’s your astronomy lesson for today readers. Tune in to this channel next week for another winter topic, such as snow shoveling. Meanwhile, I’m going to put on a heavy coat, and break out the 8” Reflector for a peek at Venus on Monday morning. It will be in half phase and very observable. Maybe someone on Venus will be doing the same! I had better wave!!

Originally written on Jan. 9, 2011.

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