If things work out well, 2013 may wind up going into history as "The Year of the Comet." There will be not one, but two naked-eye comets gracing our skies. The one that has the most potential to be truly memorable - C/2012 S1 (ISON) - will attain its peak visibility in November and December. The other one - comet C/2011 L4 (PANSTARRS) - will be visiting this month.

As its designation implies, this comet was discovered in 2011. At the time, it was still between the orbits of Jupiter and Saturn, and its brightness that far from the Sun gave hope that it would be exceptional by the time it reached the inner Solar System. The term PANSTARRS refers to the automated telescope survey - Panoramic Survey Telescope and Rapid Response System, based in Hawai'i - that first detected the comet. It didn't take long to pin down the orbit of the comet, but its brightness and overall size are - as with all comets - notoriously hard to predict. The comet could still "fizzle" and wind up being a dud. So what are its prospects?

The comet will be closest to Earth on March 5th; at that time it will be 1.09 AU (163 million kilometers, or 101 million miles) from our planet. On March 10, the comet will reach perihelion just 0.3 AU (45 million kilometers, or 28 million miles) from the Sun; this is when the comet should be at its brightest. Again, brightness estimates are often unreliable, but the latest predictions call for the comet to reach a modest magnitude 3. On that evening the comet will be 15° due east of the Sun, and thus will set a whole hour after sunset. Make sure you have a good view of the western horizon, as the comet will be fairly low by the time the sky gets dark enough to spot it.

The best time to view the comet for Northern Hemisphere observers is from March 8 - 20, especially March 12 - 17, when it is low in the west just after sunset. On the 12th - 13th, a thin crescent Moon passes to the north of the comet. Also on the 12th, the comet passes just 24 arc-minutes from the planet Uranus; you may be able to see this event with binoculars. The comet begins to dim rapidly through late March and April. It will be no better than a 5th-magnitude object by April 19, and will have dipped to below naked-eye visibility by May 1. By July 1, it will have faded to magnitude 11 and will soon be beyond the reach of the casual observer.

Comet C/2011 L4 (PANSTARRS), March 10, 2013, at 7:00 pm EDT.