Starry Night planetarium software predicts Comet PanSTARRS and the crescent moon could look like this low in the western sky at 8 p.m. March 13. We’ll just have to wait and see whether that actually happens.

Jimmy Westlake / Courtesy

Starry Night planetarium software predicts Comet PanSTARRS and the crescent moon could look like this low in the western sky at 8 p.m. March 13. We’ll just have to wait and see whether that actually happens.

Jimmy Westlake: Get ready for Comet PanSTARRS

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Jimmy Westlake

Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.

Find more columns by Westlake here.

Comet PanSTARRS (officially C/2011 L4) is bearing down on the Earth and the sun right now, coming at us from the distant Oort comet cloud on the edge of our solar system. Named for the Panoramic Survey Telescope and Rapid Response System atop Haleakala volcano on the island of Maui, Comet PanSTARRS is the first of a potential trifecta of bright comets coming in 2013. It has the potential to become a naked-eye spectacle in March, something that we’ve not seen in the Northern Hemisphere in many years.

Because comets are made mostly of ice, the closer a comet comes to the sun, the more its ice vaporizes and the brighter the comet can get as it puffs up and grows a long tail. This comet will pass very close to the sun.

Comet PanSTARRS will pass about 100 million miles from Earth on Tuesday and then some 28 million miles from the sun’s surface March 10. That’s closer than the scalding-hot planet Mercury gets to the sun. Then it rounds the sun and moves north into our early evening sky as it heads back out to the Oort cloud.

On the evenings of March 12 and 13, Comet PanSTARRS will appear close to the thin crescent moon after sunset. If the comet survives its scrape with the sun, it might present an unforgettable view on those nights. Start scanning the western horizon early because by 8:30 p.m., the comet will have set. The prime time will be from 7:45 to 8:15 p.m. If the comet grows a long tail, it might extend up and behind the moon on March 13 and remain visible even after the head of the comet sets at 8:30 p.m.

Comet PanSTARRS spent January in the Southern Hemisphere lagging behind even the most pessimistic brightness projections. Then in mid-February, it brightened considerably and now is at the threshold of naked-eye visibility.

No one can predict accurately the behavior of a comet weeks before it arrives. Comet PanSTARRS could crumble and fizzle out as it rounds the sun, or it could hold together and briefly become one of the brightest objects in our sky. It is the unpredictable nature that makes comets so fun to watch. Enjoy it because Comet PanSTARRS won’t be back for 110,000 years.

Learn more about Comet PanSTARRS and other bright comets heading our way this year at a free astronomy night program sponsored by the Colorado Mountain College SKY Club at 7 p.m. March 6 in the CMC auditorium. If the weather is favorable, telescopes will be set up for observing after the indoor program.

Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. Check out Westlake’s astrophotography website at www.jwestlake.com.

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