Pan-STARRS - the Panoramic Survey Telescope and Rapid Response System - is an array of telescopes and cameras surveying the sky for potential near-Earth objects that may impact our planet. It's very good at picking out things like new comets moving into the inner solar system (this comet will not impact us!). Since comets are named for their discoverers, this one was named for the telescope. The "C/" indicates it's a non-periodic or long-period comet - one not seen in the inner solar system before. After this approach, it won't come back for another 100,000 years or so. The "L4"means it was the 4th comet discovered in the second-half of June (A is the first half of January, B the second half, C the first half of February, D the second half, etc.)
Pan-STARRS telescope atop Haleakala
Most people don't realize that comets are rather routinely discovered these days (we know of over 4,000). It is, however, rare that a comet becomes bright enough to be a naked-eye object in the night sky. We may see two of them this year! The brightest will (hopefully) put on a show in November (see C/2012 S1 (ISON)). The other, however, is C/2011 L4 (PANSTARRS), and it should be visible in just two months as it reaches perihelion (its closest approach to the Sun).
Professional and amateur astronomers are already tracking this comet as it brightens with each day as it moves into the inner solar system. By mid-March it should be visible in the western sky just after sunset (around 7:30 pm EDT or so). Whether it will be a fuzzy, hard-to-see smudge in the western twilight or a bright, dazzling comet with a long tail is difficult to say at this time. I've seen estimates of its brightness ranging from +1 (brighter than the stars in the Big Dipper) down to -4 (the brightest that the planet Venus gets).
View to the west from the mid-Hudson Valley on March 15 at
7:30 pm DST. The comet will be to the left of the setting
Great Square of Pegasus and setting as the twilight fades.
Maybe it will even look something like this:
We'll just have to wait and see. Just keep in mind an oft-quoted quip attributed to astronomer David Levy (co-discoverer of Comet Shoemaker–Levy 9): "Comets are like cats; they have tails and do whatever they want to do."