Sunday, 18 November 2007

Don't Miss This Amazing Sight!

The e-mail came from Bill Watson, a retired Buffalo science teacher who divides his time today between bird watching and astronomy. In astronomical circles, Watson is best known as a world class recorder of meteor showers, but his message this time called my attention to a remarkable comet whose sudden outburst has made it visible to the naked eye.

This extraordinary solar phenomenon is called Comet Holmes or officially Comet 17P/1892 V1. Alan MacRobert of Sky and Telescope astronomy magazine called its appearance “an extraordinary event not to miss.”


Despite our recent series of clear skies, I couldn’t follow up Watson’s suggestion until a few days ago. But then when I searched the sky, there was the comet, a kind of blurry smudge, quite distinct in appearance from the nearby twinkling stars. My eyes are not good and there is a great deal of light pollution in my neighborhood; even so, I could see it with naked eyes. With binoculars, I could then make out much greater detail.


You too can see Comet Holmes and it does not take previous knowledge of astronomy to find it. I hope that many families will venture out on a clear night to observe it because this comet should not be missed. One California observer said of the comet: “I think this is about the most amazing thing I’ve ever seen in the sky.” I hope it will serve as a stimulator of astronomical interest among school-age kids.

Here’s how to find Comet Holmes in the evening sky. Start by facing northeast and locating one of the most recognizable constellations, Cassiopeia. This five-star constellation will be almost overhead.


The stars of Cassiopeia form a pattern that looks like a “W” turned on end. (Star maps connect the stars to make the pattern more apparent. Remember that the real stars are not so joined.) You should have no trouble finding this constellation as those five stars are much brighter than other nearby stars. I learned this constellation as Cassiopeia’s chair and, when it is seen sideways, it does have the appearance of a kind of folding deck chair.


Now look down and to the right of Cassiopeia to find the brightest star in that part of the sky, the star Capella.


Half way between the constellation Cassiopeia and the star Capricorn is another constellation, this one called Perseus. Find Mirfak, the brightest star in this constellation. Close to that star you’ll see Comet Holmes.


It is easy to distinguish the comet from the stars. The comet is blurry, whereas the stars twinkle. If you can do so, look at the comet through binoculars or a telescope. That way you may even see the beginnings of a tail, which a few astronomers have already noticed.


Comet Holmes was discovered on Nov. 6, 1892 by London astronomer Edwin Holmes. Looking for a distant galaxy with which he was familiar, he was heard by his wife to exclaim, “There is something strange here.” And indeed there was an undescribed comet. Because Holmes first identified it, the comet was named for him. (Note that the comet was not named for Sherlock Holmes, the man you might have expected since a Watson called my attention to it.)


The elliptical path of the comet was worked out based on careful observations. Astronomers showed that it would approach no nearer than 190 million miles from the sun. Since the Earth is 93 million miles from the sun, we are not threatened by any possible impact. Their calculations also showed that the comet would reappear approximately (but not necessarily be seen) every seven years.


On this approach, it was first located in July when it was visible only with powerful telescopes. But suddenly in mid-October, it became much brighter. It is now visible without a telescope. Although blurry, it is about half as bright as the nearest star. It will probably dim over the weeks ahead.


One thing that is impressing astronomers is the fact that, as one observer described it, “Comet Holmes’ luminous area is now greater than the huge area encompassed within the moon’s orbit around the Earth.

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