Beginner’s guide to Orion


By Tom Burns - Stargazing



One of the great ironies of the holiday season is that a whole lot of telescopes end up under trees but few of them get used until May. It’s hard to point a ‘scope when your feet are frozen to the ground.

One way to maximize your observing pleasure in winter is to carefully plan your stargazing session. One technique is the time-honored method of “constellation mopping.” Take a familiar star grouping and work your way through it.

Orion is a good starter constellation for all you newbies out there in telescope land. Even the smallest of department-store telescopes will show a few objects in Orion.

Let’s find it first. Look south just after dark. You’ll see a line of three bright stars, which form the belt of the Hunter. The bright stars above the belt represent Orion’s shoulders. The reddish star on the left is the old supergiant called Betelgeuse.

To the right is Bellatrix. Orion’s feet are called Saiph, to the left, and Rigel, to the right.

The first object to look for in a telescope is the multiple star system called Sigma Orionis. Find Alnitak, the left-most belt star. Sigma, the naked-eye star just below it, should split into three stars at high magnification. The main star, called Sigma AB, is really two very bright and massive stars orbiting each other so closely that you cannot split them in a telescope. Nearby Sigma D has a distinctly reddish glow. Sigma E is a bit farther from D than D is from AB. You are looking at a system of five stars, two of which you cannot see. They are all orbiting each other in a complex cosmic dance.

Two of the stars in the belt are also multiple star systems. Look for single, dim companions next to Alnitak and Mintaka, the right-most star in the belt. Whether you can see them or not depends on the clarity of the sky and the size of your telescope.

Below Alnitak and Sigma is a great binocular object, the vertical line of stars called the Sword of Orion. It resolves into a beautiful collection of stars in binoculars or a small telescope at low magnification.

In the middle of the sword is the best telescope target in the heavens, the Great Nebula. Look for a complex fuzzy cloud, a glorious mass of glowing hydrogen. The Orion Nebula is the stuff of which stars are made — a cloud of hydrogen gas and dust that is slowly collapsing into stars.

In even a small telescope, the Great Nebula reveals a wealth of detail.

I’ve observed this object hundreds of times, and I always notice some beautiful new detail each time I look.

Two long streams of light hook outward from the main patch at the center. The main portion is broken up into smaller patches by thin, dark lines. The entire area is filled with wisps and filaments of nebulosity.

At high magnification, the four stars in a rough square at the center of the nebula are called the Trapezium. Those stars are newly born out of the hydrogen gas that surrounds them.

Because they are new stars, they burn with an almost-pure white intensity.

These infant stars have perhaps another 10 billion years or so in their long lifespan.

Such stars are the most powerful continuing units of energy in creation. If all the nuclear weapons on earth exploded at once (heaven forbid), the resulting explosion would be just a momentary blip compared to the massive energies that are produced every second in the centers of the stars in the Trapezium.

Just off to the side of the Trapezium is a dark streak of nebulosity called the Fish’s Mouth. It is one of the few “dark nebulas” that is easily visible in small telescopes. It is not illuminated by any central stars like the Orion Nebula is. The fact that we can see it at all is the result of a simple cosmic coincidence. It is silhouetted against the lit background of the Great Nebula, and we see it only because it obscures the bright background.

What you are seeing is about 1,500 light-years away, meaning that it took the faint glow of light that you are seeing about 1,500 years to get here.

The obvious question is, how can we see the Orion Nebula if it is made up only of dust and hydrogen gas? The nebula is actually fluorescing. The hydrogen gas is ignited by the bright stars forming inside of it, kind of like a spark of electricity ignites the gas in a fluorescent light bulb.

Single stars are much too far away to look like anything more than a point of light in a telescope. However, a quick look at Betelgeuse, Orion’s left shoulder, will help to bring out its reddish hue.

You are looking at a star much larger than the diameter of Earth’s orbit around the sun. Estimates vary, but if our sun were replaced by Betelgeuse, the star’s girth would extend far past Earth’s orbit, perhaps brushing the orbit of Saturn.

It has lived its short, 100-million-year life burning hydrogen at a prodigious rate. It has now turned red and swelled to enormous size in preparation for its death sometime in the next 100,000 years or so. That death, called a supernova, will be spectacular. Betelgeuse will light up the night with the brightness of a full moon collapsed down to a single point.

As I have previously written, Betelgeuse has dimmed considerably in the past few months. Its relative faintness may or may not indicate that it will go supernova in our lifetimes. It has, however, made Betelgeuse look considerably redder than I have ever seen it.

It looks substantial enough in a telescope, but the density of hydrogen atoms is so low that it would be considered a vacuum on earth. Such is the simple power of fluorescence.

If you have difficulty finding these objects, perhaps the person who gave you the telescope forgot to give you a good set of star maps. I know, I know. You have a star map on your smartphone. It’s great for discovering if “that bright thing over there” is a planet or not. However, when it comes to zeroing in on specific objects and finding them in your telescope, nothing beats a larger-format, printed set of maps.

As far as star maps go, I’d recommend Guy Consolmagno’s Turn Left at Orion for all you beginners out there. With it and a telescope of practically any size, you’ll find plenty to see. Don’t forget to purchase one of those little red LED flashlights to look at the star maps contained therein. You don’t want to spoil your night vision.

Some of you are saying, “But my telescope has computer control. I’ll just use that to find things.” When you use the computerized guiding system, the object you’re viewing belongs to the telescope. When you find it yourself, it belongs to you.

Do yourself a favor. Learn the sky, and then pass on that ancient knowledge to the next generation. We humans are fleeting things when it comes to the universe. Our knowledge lives a lot longer if we pass it on.

Here’s a case in point. Some familiar objects will be beyond the capability of your ‘scope. Many folks have seen the images from the Hubble Space Telescope of the Horsehead Nebula, for example. A few know that it is located within Orion’s boundaries.

In my own quest to see the elusive Horsehead, I built larger and larger telescopes until I finally had one that barely fit in my car. I bought special filters and headed for the darkest sky I could find. Finally, several thousand dollars later, there it was — a faint wisp of light with a tiny dark notch in it.

The quest was noble, I suppose, but, frankly, stupid. During that period, my children had to do without luxuries like shoes. I am truly convinced that if astronomers ever discover the other end of the Horsehead, they’ll name it after me.

As a relative newbie, I never would have found the Horsehead on my own. Luckily, I was observing that cold, cold winter night with a seasoned observer. John very patiently showed me the steps to find it. How my heart leaped when that little notch of darkness edged into view.

John got a bad case of frostbite in his hand that night, but he loved to tell the story of my youthful enthusiasm anyway. Whenever he did, he would flex his fingers slowly. With a grimace of joyful pain on his face, he would say, “Yeah, but it was worth it.”

Long ago, John moved out of town to take a teaching job, and I don’t know whether he is alive or dead. But I do know that the memory of John and that night lives on in me. And when I am gone, perhaps it will live on in you.

I hope that some night soon, you will make a few memories of your own. The first step is to bundle up and go outside. A universe of memories awaits!

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.