Learning to see


By Tom Burns - Stargazing



As winter turns to spring, I always get a few calls from people who are finally emerging from their winter cocoon with Christmas telescopes clutched in their hands.

Their first experiences are inevitably disheartening. They either can’t figure out how to use their new computer-controlled telescopes, or they are painfully disappointed in the views they are getting.

Winter is a tough time to observe the sky. The occasional clear night is often frigid. Even the hardiest telescope owner doesn’t want to travel farther than their own backyard to lug equipment out into the cold and dark.

For most of us, light pollution from city lights makes finding worthy astronomical objects difficult. With the exception of a few winter constellations, like Orion or Taurus, even the basic star patterns are difficult to identify.

Most stargazers soon realize that a trip or twelve into rural Ohio is their only recourse. But then a new question arises. Where can you go that won’t trigger frostbite or a visit from local law enforcement? (That’s no joke, gentle readers. I speak as someone who has had the latter, rather unsettling experience more than once.)

For starters, I’d recommend joining the Columbus Astronomical Society (CAS). They specialize in teaching newbies the ins and outs of their telescopes. Besides, they have cultivated relationships with observing locations like Perkins Observatory locally and the John Glenn Astronomy Park to our south.

CAS meets every second Saturday of the month at Perkins. For more information, check out https://columbusastronomy.org.

As newbies gain a little experience, a new problem arises. They soon realize that amateur astronomy has a long learning curve.

As with any worthy endeavor, it takes time to become a proficient stargazer. Even the smallest telescopes and binoculars are spaceships to other worlds, but you have to learn how to run the controls.

Most of all, you have to train your eyes and heart to see. Your initial views of star clusters and galaxies are inevitably disappointing. They look at first like balls of lint. Where are all the details visible in those long-exposure photographs that fill the pages of the coffee-table astronomy book you got for Christmas or appear daily on Astronomy Picture of the Day on the Internet?

The details are there, oh ye frustrated stargazers. The longer you look, the more you will see. Your eye will never match the images taken by the Hubble Space Telescope. However, the direct experience of the sky and all the wonder contained there is far more emotionally and intellectually satisfying than simply flipping through a book or surfing the Web.

A case in point is the star cluster designated as M35 in the Messier Catalog of deep-sky objects.

A deep-sky object is anything outside our solar system. The catalogs of these astronomical splendors tend to include everything that isn’t a star and appears at first as a fuzzy patch in astronomical instruments of small size.

M35 is easy to find and makes a great introduction to this “harder” class of telescopic objects. Of course, you can save yourself a lot of trouble by going to one of the programs at Perkins Observatory. (Go soon. M35 won’t sit above the horizon forever.) You can also use that fancy “go-to” computers attached these days to many telescopes.

Or you can do what humans have done throughout most of their history. You can learn the sky and gain the simple but profound pleasure of cosmic familiarity. The nighttime sky is also beautiful beyond measure, especially if you see it from a dark, rural locale far from city lights and know it well enough to identify a few constellations.

Of course, you’ll need a decent star map, many of which are available as apps for your smartphone, tablet, or laptop. You can also break down and go to a bookstore (remember those?) and buy one on paper (remember paper?). Grab an inexpensive red LED flashlight so you don’t ruin your night vision, and off you go.

Just after dark, look for the constellation Gemini high in the southwest. You’ll see two bright stars, called Castor and Pollux, of equal brightness, huddled fairly close together. Two parallel strings of bright stars extend to the south from Castor and Pollux. Follow the upper string and hang a left.

In binoculars, you will see a smallish, round blob of light. You’ve found M35.

Don’t look away. Try to catch the light patch out of the corner of your eye, a technique stargazers call “averted vision.”

Look just to the side of it, and view the light with your peripheral vision. After a time, the light will look lumpy, with patches a little brighter than the rest. The blob is now a structured blob.

Now turn to your telescope. Even in a small instrument, the blob will resolve into a few bright stars caught in an unresolved haze, especially if you use your averted vision.

You see so little because your brain is drawn to what is most easily seen. You must trick your mind to see more.

Use your peripheral vision again. Slowly, you will see more and more stars as your eye trains itself to see what’s really there. Eventually, you will see at many as 50 stars surrounded by the haze of hundreds of unresolved stars that fill the spaces among the brighter points.

But don’t stop there. You have learned to see, but the process has just begun. Now consider what you are seeing.

M35 consists of several hundred stars crowded in a region about 30 light-years (180 trillion miles) wide. It is perhaps 2,800 light-years distant. The cluster was born only 50 million years ago, a snap of the fingers compared to our five-billion-year-old sun.

Most of the stars are hot and blue, meaning they are newly formed from the enormous hydrogen cloud that gave them birth.

A few of the stars are yellow or orange. They are giant stars that have already reached maturity and beyond. Having lived a quick and violent life, they will soon perish.

Now, grab a book on the subject and dive even deeper.

M35 is the 35th object in Charles Messier’s catalog of fuzzy things. Messier was searching for comets and got annoyed with all the patches of light that were not comets but looked like them. He created a list of these “non-stellar” objects.

The credit for M35’s discovery goes to Philippe Loys de Cheseaux sometime during 1745- 46. Using a small telescope, he saw a hazy patch that really did look like a comet. By 1864, telescope technology had improved enough that Messier resolved it into a “cluster of very small stars.” Today, even a small, department-store telescope reveals 10 or so bright stars woven into a milky cloud of light.

Keep looking, though. The hazy patch consists of unresolved stars just beyond your eye’s ability to resolve them. Look slightly to the side of the patch and catch it out of the corner of your eye. (Astronomers call this technique “averted vision.”) Slowly, as your eye adapts, more and faint stars will pop out of the haze. You might see as many as 50 stars in one of the most stunning views the sky has to offer.

Further examination will reveal even more. You’ll notice that most of the stars have a slightly bluish cast. A few look distinctly red or orange. That simple piece of information allows us to estimate the age of the cluster.

Young stars exist in clusters because they are born in enormous clouds of gas and dust called nebulae. Stars are balls of exploding hydrogen that condense by gravity from a given cloud. The stars in a cluster often formed within a few million years of one another as the denser parts of the cloud collapsed into spinning balls.

A nebula starts out tens of trillions of miles wide. The stars in it might look close to one another, but they are far enough apart not to be bound by one another’s gravity. Eventually, their random motion and the gravity of the other stars of the Milky Way will draw them apart. For now, they are still young enough to be grouped together.

But how young? To find out, we must ferret out the evidence that our observations provide. Really young clusters still have vestiges of the gas that formed the stars surrounding them like a cocoon. Here, it is helpful to look at an image of M35 taken with a large telescope.

No such gas is visible in M35, so it must be getting on in years. However, stars early in their lives tend to burn with a hot, blue flame, and blue stars dominate M35. Still, a few reddish stars as visible, and that’s a sign that some of its stars have reached old age.

We conclude that M35 is young, but not in its infancy. Very large stars reach old age prematurely in a few tens of millions of years and cool to a rather tepid red. The number of red stars in M35 indicates that it must be about 80 million years old. The gas of a nebula coalesced into this star cluster a snap of the cosmic fingers ago when dinosaurs ruled Earth.

Learning to see is more than a trick of the eye. When you know at last what you are seeing, when you learn the meaning hidden in the light of the stars, only then will you be transported to distant worlds.

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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.