Comet Pan-STARRS Visible this Week

When it was last in our corner of the planetary neighborhood, dinosaurs walked the Earth.

Comet C/2011 L4 has been tumbling towards the sun from the outermost reaches of the solar system for tens of millions of years. 

Better known as "Pan-STARRS" in honor of the Hawaii-based telescope that discovered it two summers ago, the comet is back for a limited engagement.

Having made its closest approach to the sun on Sunday, Comet Pan-STARRS will, weather permitting, be visible low in the western sky in the fading light after sunset this week.

The comet is not expected to be especially bright to the naked eye. A pair of binoculars or a small telescope could help you spot its contrail-like smear in the hour or so before it follows the sun over the horizon.

According to DC Agle of NASA's Jet Propulsion Laboratory, Comet Pan-STARRS will remain in our skies throughout March, becoming gradually fainter as April approaches.

Relics from the earliest days of the solar system, comets have been called "dirty snowballs" of ice and rock. As they approach the sun, the sun's heat and the erosive effect of the solar wind dislodge particles from the surface of the comet, creating a highly reflective stream of debris pointing away from the sun. This is the comet's "tail."

The most famous comet, Halley's Comet, orbits the sun about once every 76 years, last visiting in 1986. Some "short period" comets have orbits that only take a few years. Given its aeon-long journey, Comet Pan-STARRS is believed to have originated in the Oort Cloud, a theoretical junkyard of comets and other interstellar debris hovering about a light year away, on the very edge of the sun's gravitational pull.

If you do spot Comet Pan-STARRS and find it disappointing, hang in there―the much brighter Comet ISON is expected later this year.