About a year from now, Comet ISON may become the brightest comet that anyone alive has ever seen. It will be the greatest astronomical event of next winter. But one caveat: How bright any comet gets is always somewhat uncertain, and this one is now receiving vigorous analysis among planetary astronomers and comet experts.
Two Russian astronomers, Vitali Nevski and Artyom Novichonok, discovered the comet on September 21. They used a 16-inch reflector telescope of the International Scientific Optical Network, whose abbreviation, ISON, has thankfully been made the official name of the comet. Otherwise we would have had to deal with “Comet Nevski-Novichonok.”
Although the comet was super-faint when discovered (at magnitude 18.8, it was about 100 times dimmer than Pluto), its calculated orbit will carry it extraordinarily close to the Sun, and then a few weeks later, very close to Earth. At the end of November 2013, the comet will approach to a mere 1.1 million miles of the Sun, or 30 times closer to the Sun than the charbroiled planet Mercury. This should not quite destroy it, but instead cause much of its ices to sublimate into a spectacularly long tail, releasing trapped pebbles and dust that will also spread out for a million miles or more. Unfortunately, it will then hover only 4.4 degrees north of the Sun, and it will probably be unseen in the solar glare.
Immediately after reaching this solar near-point, or perihelion, Comet ISON heads in a direction optimally favorable for us: north. Developing an ever-greater, even-more-spectacular tail, it should be as bright as Venus, and may even cast shadows! We in the Northern Hemisphere will get the best views as Christmas approaches. Then, on January 8, 2014, the comet passes just two degrees from Polaris, the North Star, as it zooms just 37.2 million miles from Earth.
A “Great Comet” like this impending Comet ISON arrives every 15 to 20 years on average. The last one was Comet McNaught in 2007, which was the brightest comet in 40 years. Unfortunately for us, it was seen only in the Southern Hemisphere, and we didn’t even get a glimpse of it. This new one will have opposite characteristics: It won’t be seen in Australia at all.
Before that, we had the odd circumstance of getting two great comets in consecutive years, with Hyakutake in 1996 and then the brilliant, universally observed Hale-Bopp in 1997: the brightest comet in decades. Because it’s now 15 years since that one, we are “due.”
This is very exciting.