Now that we’ve had our fill of asteroid action for a while, let’s look forward to something a little calmer that’s heading our way this year. Two very bright comets are on the horizon, and one later this year could be the brightest in recorded history. I was fortunate enough to stand in the Arizona desert in 1986 and see Haley’s Comet, and I’m hoping that 2013 will be just as memorable.
Pan-STARRS (Comet C/2011 L4) will be its brightest on March 10 and will hang around until about the middle of April. After swinging around the sun, Pan-STARRS will pass through the constellations Pisces and Andromeda, and will be perfectly positioned for us to see here in the Northern hemisphere. It is expected to be visible to the naked eye and should have an impressive tail.
But the real excitement is building for ISON (Comet C/2012 S1). On Nov. 28, ISON will pass within 680,000 miles of the surface of the sun, much closer than Mercury. Because it is passing so close to the Sun, it is hoped that large quantities of ice and dust will boil off and give us an impressive show. ISON may even be clearly visible during the daylight hours during the days leading up to Christmas. Well, unless the Sun breaks it into pieces first.
Although there are always comets in the sky, most of them pass too far away from the sun to develop large, visible tails. The nuclei of a comet is primarily made up of ice, dust and small rocky particles, and when it gets close to the Sun, the Sun’s heat vaporizes the ice of the comet and blows the ice and dust away with the solar wind – which is why a comet’s tail always points away from the sun.
Fortunately, we haven’t heard anything about either comet passing too close to the Earth for comfort. I mean sure, Jupiter was hit back in 1994 by Comet Shoemaker-Levy, and again in 2009 by another comet that left a bruise about the size of the Pacific Ocean. But hey — we’ve got nothing to worry about, right? (Note: See earlier Bruce Willis entry).