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Tuesday, February 5, 2013

Brad's Sky Stuff

The Year of the Comet

As far as celestial events go, 2013 may very well be a year for the history books. 

Two comets swing into the inner solar system this year, one next month and the other at the end year.  Both comets have the potential to reach naked eye visibility.  But the second may be bright enough to view during daylight.

What exactly is a comet anyway?  Comets are best described as dirty snowballs orbiting the sun at the outer edges of the solar system in a huge cloud known as the Oort Cloud.  When nudged by the gravity of a passing star, they are hurled in long elliptical orbits around the sun.  As the comet nears the sun, it’s icy material melts, forming an enormous tail of gas and dust.  Sometimes comets brighten so much they can be easily seen with the naked eye. 

We begin with Comet PanSTARRS, which was discovered by the Pan-STARRS telescope in Hawaii in June 2011.  Throughout February, this comet is only visible in the southern hemisphere.   But in early March, PanSTARRS whips around the sun becoming an evening object for Northern Hemisphere observers.  It will grace the western sky after sunset from March 10 through the end of the month. 

If we’re lucky PanSTARRS may reach naked-eye visibility and sport a wispy tailing extending upward.  The problem with comets though, is that they are notoriously unpredictable.  It may be a breathtaking object or it may be a dud.  Time will tell.  In next month’s article there will be more details on how to observe PanSTARRS and by then we hopefully will have a better sense of how bright the comet will be. 

The real showstopper comes toward the end of 2013 in Comet ISON.  Discovered last fall as a very faint object in the cold depths of the solar system, this comet has a date with the sun on Thanksgiving Day.  ISON will graze the sun’s outer atmosphere, passing within a mere 680,000 miles from our star’s surface!  If it can hold together, and resist being torn apart by the sun’s immense gravity, it should emerge as a stunning object possibly brighter than the full moon.  Such magnitude would make ISON visible during the day!

Some are already calling Comet ISON the “Comet of the Century.”  But the unpredictability of comets can’t be overstated.  It could be a let down, as other comets have been.  In any case it is one to watch and you can bet that space enthusiasts around the globe will closely follow Comet ISON’s progress.  We at the Cosmosphere will as well.  Stay tuned for opportunities to observe with us.