By CHRIS STEPHAN
Special to the News-Sun
The last two great comets to grace our night sky were Comet Hyakutake in March 1996 and Comet Hale-Bopp in April 1997. Most comets are chunks of ice and rock that reside in the deep parts of our solar system past Pluto. This is the home of the comets, the Oort Cloud. When they get snatched by our sun's gravity, they begin a long journey of millions of miles toward our sun.
As a comet nears our sun, especially Earth's distance and closer to the sun, it forms a tail that points away from the sun. This is caused by solar particles streaming outward from the sun, warming the comet. The melting comet's particles stretch away from the comet in the opposite direction of the sun.
The first comet that is on its way is called Comet Pan-STARRS. It was discovered in June of 2011, so it is being well tracked by professional and amateur astronomers worldwide. It is still quite dim, but the real show will begin in early March, 2013. The comet will be at perihelion March 10 or 11, meaning it will be closest to the sun. On March 10 the comet will be visible for us in the northern hemisphere.
The comet, at its brightest, will appear 15 degrees from the sun. The size of your fist at the end of your outstretched arm is about 5 degrees, so three fist lengths would be 15 degrees. However, it should stay bright for several days. It is not possible to tell at this point how long the tail will be. If it is short, it may be a bit harder to see. However, if the tail is longer, it will point up high from the western horizon right after sunset.
To view this comet, find a place with a clear, unobstructed western horizon. Just make sure you are facing west toward the sunset point in the sky. I would suggest place such as out toward the Bombing Range that has a low west horizon, or east of Lorida out to the Kissimmee River. It is very dark out there, and there a plenty of places with good low western horizons.
You may want to use binoculars if you cannot see the comet with the unaided eye. Please wait until the sun sets completely so you do not accidentally look at the sun and hurt your eyes. Once you spot it, then take the binoculars away and see if you can see it with just your eyes. Once you have found the comet, if you have a telescope with you, zoom in on the details. I can promise you the view with the eye or binoculars will give a beautiful view, if the comet lives up to the predictions for its brightness.
March 13-20 will be the best date range for viewing the comet.
I plan on having a night sky viewing event during this date range for our students at Avon Park High School, their parents, and the public. I hope to hold it out towards the Bombing Range. As the date draws closer, the exact location of the viewing event will be announced in the News-Sun.
The next comet will appear later in the year in the early night sky shortly after sunset. This comet is called Comet ISON. This comet was discovered on Sept. 24 by two observers, one in Belarus and the other in Russia. All indications so far hint that Comet ISON will be an even greater object that Comet Pan-STARRS.
This comet is inbound from the Oort Cloud. Predictions right now show it passing just 725,000 miles from the sun. That is very close. That should cause a much brighter comet and possibly a much longer tail. If the comet survives this close approach with the sun, this comet could put on a spectacular show. This is the big "if" -- will it survive that close of an approach with the sun?
The comet should be visible to the unaided eye from early November 2013 through mid-January 2014.
As the time gets closer for the appearing, I will make sure that updates will be announced in the News-Sun. You could actually use the same locations to observe both comets.
I will also try to have updates posted on the APHS website at http://www.highlands.k12.fl.us/~aph/
Let's hope these comets really put on a show. These are rare events and ones to share with family and friends.
Chris Stephan is an earth/space science teacher at Avon Park High School.
Sunday, December 30, 2012 - www.newssun.com/123012-comets