Watch The Skies For Comet Pan-STARRS Later This Week; ISON Comes In November

Look to the West later this week, and you may be able to see something no one on Earth will ever see again for more than 100,000 years.

The comet Pan-STARRS -- named after the telescope in Hawaii that discovered it in 2011 -- is on a steady course to fly by our planet and give Earthlings a bit of a show. People in the Southern Hemisphere have already been able to see the comet, which makes its closest approach to Earth on Tuesday. But now it’s the Northern Hemisphere’s turn.

North of the equator, Pan-STARRS will be visible to the naked eye starting on Thursday, when it will appear very low in the horizon just after the sun sets. On March 13, the comet will pass under a thin crescent moon, which will likely make for some neat pictures.

To see the comet, it’s best to find a dark spot, away from street lights, with an unobstructed view of the western horizon. Turn your eyes to the horizon just after the sun sinks. Pan-STARRS might just look like a star to the naked eye, but if you have binoculars, you’ll be able to clearly see its shiny tail.

The brightness of celestial objects is rated on a magnitude scale, with brighter objects indicated with lower numbers. Unassisted by a telescope, the human eye can see anything with a magnitude rating of 6 or lower. By comparison, the bright North Star, Polaris, is rated a 2; the sun is a scorching -27.

In February, scientists from the Institute for Astronomy in Honolulu said they expected that Pan-STARRS would get about as bright as the stars in Orion’s belt or in the bowl of the Big Dipper, a magnitude rating of between 2 and 3. Since then, new observations have prompted scientists to revise that rating, saying Pan-STARRS could get up to magnitude 1.

Pan-STARRS’ full official name is Comet C/2011 L4 (PanSTARRS). As Alan Boyle at NBCNews explains, the “C” part of its name means the comet is fairly young, making its first trip from the edge of our solar system toward Earth. “L4” means that Pan-STARRS was the fourth comet scientists discovered during the first half of the month of June.

By April, Pan-STARRS will no longer by visible to the naked eye. Scientists think it’ll be about 110,000 years until the comet swings around our way again, so get your viewing in while you can!

An even more dazzling celestial light show is on schedule for November, when the comet ISON is forecasted to outshine even the full moon (which has a magnitude rating of -13). ISON will pass extremely close to the sun -- 1.1 million miles -- on Nov. 28, earning it the title of a “sungrazing” comet. Even after ISON leaves our view, pieces of it will remain behind in Earth’s orbit, and when we pass through the comet’s debris in January 2014, a new meteor shower could come into being.

While Earth is enjoying comet flybys in 2013, 2014 could be an ominous year for Mars. Newly discovered comet C/2013 A1 (Siding Spring) is set to give the Red Planet a close shave in October 2014, and it’s unclear whether the comet will fly by safely. The comet could pass 650,000 miles over the Martian surface, or 63,000 miles above, or -- though the odds are small -- slam into the planet at 126,000 miles per hour.

According to the Jet Propulsion Laboratory, the latest observations of comet Siding Spring peg the chances of an impact with Mars at about 1 in 600, though those odds should come down even more as scientists make more observations.

Still -- stay safe, Curiosity!