Sunday, November 05, 2006

Dr. Ken Rumstay's SPIRAL CORNER

OBSERVER'S NOTEBOOK

A century ago, the Milky Way would have been familiar to all but the few who lived in the largest cities.

Most Americans of the era would have been able to point out at least a dozen constellations.



Today, a plethora of electronic diversions --- including the internet --- keep us indoors at night. For those who do venture outdoors, light pollution has washed the Milky Way out of most of our skies.

The end result is that few people today have the time or inclination to study the night sky. Yet stargazing is still loved by a hardy minority of millions!

To share in the fun, there’s no need to spend thousands on fancy equipment; in fact, there’s no need for equipment at all.

In my astronomy classes here at Valdosta State University, I always have my students observe the heavens for at least a week before hauling out the telescopes.

This column will provide tips on how to get the most out of your night sky. All that’s required are two good eyes and a clear sky.

The first thing you’ll notice about the night sky is that it’s dark! That seems obvious. But as Heinrich Olbers pointed out in 1823, this actually tells us a lot about our universe.

Without much evidence to the contrary, 18th century astronomers and philosophers believed that the universe in which we live was infinite, and had always existed.

In other words, the universe had no boundaries in space or time but Olbers pointed out that if this were true, then the universe would contain an infinite number of stars, and in whatever direction we chanced to look, our line of sight would eventually intersect the surface of one of those stars.

If so, then the entire sky would glow as brightly as the surface of the sun! This is obviously not the case, and cosmologists have since validated the theory of the big bang in which the universe had a definite beginning, forming some 14 billion years ago.

Because of Olbers’ Paradox, you’ll notice how dark everything really seems once you’re outside under a night time sky. Gradually as your eyes adjust and begin to dilate, you will notice gradations in brightness until your eyes are able to discern darkness.

Astronomers refer to this process as “becoming dark adapted,” which takes about five minutes for a typical adult.

Once you’ve learned the lessons of taking the time to allow your eyes to fully adjust to the night sky, then believe it or not, if you’re still not convinced that you can observe the cosmos without a piece of astronomical equipment, then the first thing to buy would be a small flashlight.

Buy one small enough to hold in your mouth. That may sound crazy or even unsanitary, but it’s a skill that you will find handy later on.

The lens of your new flashlight should be covered with some red translucent material. Since red light tends not to overpower human night vision like light from other parts of the spectrum, both amateur and professional astronomers use it to avoid killing themselves in the dark and to avoid diminishing their “dark adapted” night vision.

Plastic report binders from office supply stores typically sell translucent red covers that can be fashioned at the end of one’s flashlight. If that’s too hard to track down, then red cellophane or even painted-on red nail polish applied to the flashlight lens can do the trick.

In some cases, the head of the flashlight can be disassembled to allow the filter to be placed against the inner surface of the lens. If not, simply secure it into place with double-sided adhesive tape.

If observing near your own house, turn off all your outside lights and if you can convince the neighbors to join you, have them do the same. Leave the house, and use your newly fashioned red light flashlight to make your way to a spot clear of obstructions from nearby trees or buildings.

Turn off your red light, wait five minutes or so, and look upwards. Towards the north, you should be able to see the Big Dipper, the most famous and most easily recognized set of stars within any of the constellations.

Depending on the date and the time of night, the Dig Dipper may be rightside-up, upside-down, or standing on its handle. But it is always in the northern sky. In November and December it is rightside-up. But at its lowest point; if you live in the southern United States, it may be obscured by trees or buildings.

Higher in the northern sky, you will see five stars, easily visible but not terribly bright, which form a shape not unlike the letter “M.” That’s the constellation of Cassiopeia, the Queen of Ethiopia, seated on her throne.

Now turn towards the west. High in the sky are three bright stars which form the so-called “Summer Triangle.” The Summer Triangle is not a constellation. Its three stars are each the brightest stars in three separate constellations.

The star at the top of the triangle is Deneb; hanging down from it (and tilted at a slight angle to the left) are stars which form the shape of a cross. This is the constellation of Cygnus the swan, although the pattern is also commonly known as the Northern Cross.

Below Deneb is a much brighter star called Vega. Vega belongs to the constellation of Lyra the harp; the other stars in Lyra form a parallelogram to the left and slightly above Vega itself. These stars are faint; you may have difficulty seeing them if your sky is not very dark.

To the left of Vega, is the bright star Altair. Altair belongs to the constellation Aquila, the eagle. But it in now way resembles an eagle! At least I’ve never seen an eagle in it.

Next time, we’ll look at some of the constellations rising in the east at this time of the year. There are many myths and legends immortalized in the night sky, and they are accessible to everyone!

Image: courtesy Roger Smith/NOAO/AURA/NSF

1 Comments:

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12:51 AM  

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