March 6, 2013
Comet PANSTARRS: Coming To A Backyard Near You This March
Lee Rannals for redOrbit.com - Your Universe Online
This March sky gazers will be treated to another special celestial event as comet Pan-STARRS C/2011 L4 becomes visible to the naked eye in the Northern Hemisphere. According to astronomers from the University of Hawaii, the comet should become visible from about March 7 just above the horizon.
The Hawaiian astronomers say that March 13 may be the best time to take an interesting picture of the comet because at that time it will appear just below the crescent Moon. By the end of March, however, comet PANSTARRS C/2011 L4 will no longer be visible in the evening sky, but you will still be able to catch a glimpse of it just before sunrise.
As comets approach the Sun, they start to heat up, causing the ice that clings to them to transform directly from ice into a gas in a process known as sublimation. When this takes place, they develop what is known as a coma — a large envelope of gas and dust that surrounds the solid nucleus — and two tails. The coma and tails are what make comets visible to the naked eye.
Comet Pan-STARRS C/2011 L4 is on a path from the very outer reaches of the solar system. As it passes by planets, it receives a gravitational "kick" that will eventually propel it out of the Solar System. Therefore comets like this one make only a single voyage through our planetary system and will never be seen again. By comparison, other comets such as Halley's have elliptical orbits that bring them back through our inner solar system at regular intervals.
Comet Pan-STARRS C/2011 L4 will not, however, be the sole "star of the show" for the 2013 night sky events. Another comet, known as ISON, could become one of the highlights of the year. As this comet approaches in November, the sun's atmosphere will light it up, and by later that month it could appear in our night sky as bright as the Moon. NASA said that it may be so bright as to be visible during daylight hours.
Although Comet ISON has the potential to put on a spectacular show, NASA warns that these highly unpredictable objects could also vanish without a trace. “I´m old enough to remember the last ℠Comet of the Century´. It fizzled. Comets are notoriously unpredictable,” said Don Yeomans of NASA´s Near-Earth Object Program.
“Comet ISON is probably at least twice as big as Comet Lovejoy and will pass a bit farther from the sun´s surface,” explained Matthew Knight of the Lowell Observatory in Flagstaff, Arizona. “This would seem to favor Comet ISON surviving and ultimately putting on a good show.”