Comet Holmes
Comets >
There is a comet in the sky tonight which is normally just an occasional no-big-deal visitor to our parts of the solar system, but which for some reason has made quite the spectacle of itself this time around. And it's time for you and friends or family to go out and take a look at the little show-off before it fades away.
Comet 17P/Holmes is a "periodic comet" (hence the letter P in its name). "Periodic" is just astrospeak for "it takes less than 200 years for this guy to go around the sun." Comet Holmes only takes about 7 years to make a complete circuit.
The "Holmes" part obviously is for the man who discovered it. Edwin Holmes, a British astronomer, discovered the comet in 1892 while sightseeing around the constellation Andromeda.
The comet had just had an "outburst," a phenomenon in which a comet suddenly throws out a pile of dust and gas which gets lit up by the sun. This causes the comet to brighten many magnitudes. What may have been visible only through a telescope just hours ago is now so bright it can be seen naked eye. And Holmes was the first to see it.
And that is what appears to have happened in the last several weeks to this normally inconspicuous comet. At the end of October, this tiny little critter suddenly brightened from magnitude 17 to about 2.5 in just a couple hours. Translation: what could only be seen through the best backyard telescopes could now be seen merely by looking up into the night sky.
Now how to find it. Go out tonight and first allow a few minutes for your eyes to adapt to the darkness. Then face northeast. Look up a little more than two-thirds into the sky from the horizon. There you will find a faint circular glowing cloud in the constellation Perseus. That glowball, my comet-seeking friends, is Comet Holmes.
You will not see the expected long tail of the comet. Why? Currently we are passing by Holmes in our orbit. The sun is on one side, Holmes is about 150 million miles on the opposite side. So far, no problem.
Now the tail of a comet is caused by the sun's solar winds blowing the expanding dust and gas away from the comet, out to the farther reaches of the solar system. Since we are in the line of sight, the tail is being blown away from us, not to either side. We're looking at the comet "head on."
Use a telescope or binoculars to bring out more of the details. Binoculars are enough. And keep an eye on it in the next weeks. Will it just fade back into anonymity? Will it have another outburst? Will its tail become more visible? Will its hue continue to change in subtle ways as has been observed lately?
These are all questions you can tease your young astronomer son or daughter with. Comet Holmes might be the one minor cosmic event that sends a youngster into a future in astronomy, perhaps some day to discover a comet of her own.
Until next time, clear skies!
Posted by Mark Ritter at 2007.11.19 02:00 PM | Comments (0)
