Annular eclipse gets astronomers' hearts pumping

Thursday, May 10, 2012

Nothing gets an astronomer salivating in anticipation faster than the words "solar eclipse."

Well, there are going to be a lot of slobbering astronomers for the next week or so as May 20 approaches.

That is the date for an annular solar eclipse of the sun.

A solar eclipse occurs when the moon passes between Earth and the Sun blocking out the Sun's light as we see if from Earth.

However, this will not be a "total eclipse" in the normal sense. It will be what is called an annular eclipse.

An annular eclipse happens when the moon is at a far point in its orbit and thus is not big enough to cover all the face of the sun, leaving a ring of sunlight around the edge of the moon; that ring is called an annulus.

The path of totality (as far as it can be considered total) will start in Japan early in the morning, cross the expanse of the Pacific Ocean, cross into northern California, moving on through Nevada, southern Utah, northern Arizona into New Mexico and west Texas before leaving Earth's surface.

Albuquerque, New Mexico is on the center line for totality. The eclipse will begin there at about 7:37 p.m. local time and will still be in progress as the sun sets at 8 p.m. local time.

For those of us who happen to live nowhere near the line of totality we will be seeing a partial eclipse, where only part of the sun's face will be blocked by the moon.

It will look like a giant cookie after someone has taken a large bite out of it.

Now, here is the mandatory word of warning; just because part of the sun's light is blocked does not mean it is safe to look at it without protection of some kind.

Even along the line of totality it is still not safe to look directly at the sun without some form of dimming device, like No. 15 welder's glass or a specially designed solar filter for telescopes.

The best way to watch a partial (even an annular) eclipse is to poke a small pin prick of a hole in an 8½ x 11 sheet of paper and project the image of the eclipsed sun onto another similar sized sheet of paper held below it.

Even a fraction of a second of direct solar light contact will burn and destroy the retina of your eyes. The eclipse will be the last thing you look at, ever.

So take precautions if you intend on viewing the eclipse.

SKY WATCH: Third quarter moon on May 12. Venus is still blazing in the western sky after sunset, but not for much longer. It is setting sooner after sunset each day and by the end of this month it will be gone. Even though Venus is slowing moving off the stage, ever the lovely charmer she is, there are four bright stars surrounding her to get her attention. Above and right is Capella, the brightest star in Auriga, the Charioteer. Above and left of the brothers, Castor and Pollux, and down to the left is ever-faithful Betelgeuse in Orion. Two other bright stars will be competing for our attention for the next few weeks. Low on the eastern horizon about an hour after sunset our old friend, Vega, returns for its summer in the sky. Vega is the brightest star in Lyra, the Harp, and one of the anchors of the Summer Triangle. The other bright star is above and slightly right of Vega, it is Arcturus, the brightest star in Bootes, the Herdsman. Bootes looks like a triangle-shaped kite lying on its side.

NEXT WEEK: More astronomical blathering.

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