Stargazers are certainly the beneficiaries of gravitational pull this year, especially if comet-watching is your thing, because in 2013 the Earth will play host to a set of comets, including two projected "Great Comets" -- Pan-STARRS and ISON. Space.com reported March 12 that comet Pan-STARRS is upon us and begins its best viewing days the same day. But don't worry; it's not a one-and-done deal, so there's still a few chances to to see it with the naked eye (and more if you have a telescope). But if you want to see it unaided, you'll get a chance for the next few days if you live in the Northern Hemisphere. Otherwise, it'll be a 100 million years before Pan-STARRS swings back around to our side of the Solar System.
Instructions for best viewing include a non-occluded view of the Western horizon and allowing the sliver of crescent moon be your guide. The moon will be its most visible just about 10 degrees up and to the right from where the sun sets along the boundary between Earth and sky. The comet will be about 5 degrees left of the moon. But that's on March 12.
On succeeding days the comet will cross over the moon in a slow arc as March progresses. As April arrives, according to EarthSky.org, the comet will have traveled far enough away from the sun where its tail will begin to fade. During this time, only people in the north will be able to see it. Comet Pan-STARRS will also be in the vicinity of the fuzzy stellar object, the Andromeda Galaxy.
Still, a long and showy tail may not be in the cards, so the best viewing just might be within the month of March while the Sun's heat is still affecting the amount and reflective quality of the cast-off from the comet. It is likely that March will be the only time the comet will be visible without the use of some type of telescopic aid.
Comet Pan-STARRS was discovered in June 2011 by a group of astronomers in Hawaii using the Panoramic Survey Telescope and Rapid Response System (or Pan-STARRS), from whence it got its name. It is one of two comets currently visible with the unaided eye. In the Southern Hemisphere, Comet Lemmon has been putting on a show (and for a few days, working with Pan-STARRS to form a nightly duo).
A second "Great Comet" -- so called because of exceptional brightness -- is also headed toward Earth. Comet ISON is expected to pass very close to Earth and put on a spectacular display. Expectations are so high for ISON that it has been labeled the "Comet of the Century."