Arizona astroimager Dean Salman imaged Comet ISON and several galaxies through a 20-inch telescope from Kitt Peak National Observatory. The faint galaxy below ISON is IC 2196, which glows feebly at 14th magnitude. // Dean Salman/NOAO/AURA/NSF
Two astronomers found Comet ISON (C/2012 S1) glowing dimly at magnitude 18.8 on September 21, 2012. On November 28 of this year, ISON will lie closest to the Sun — a scant 680,000 miles (1.1 million kilometers) from its surface. At that time, current predictions suggest, it may appear 500 billion times as bright as it glowed at discovery.
Throughout the spring, large telescopes may reveal Comet ISON, but it will show few details. By late summer, you can spot the magnitude 11 comet through a 4-inch telescope. Binoculars come into play in early October when ISON’s magnitude hits single digits. And sometime around Halloween, the comet should cross the naked-eye threshold for those at a dark site.
On December 8, Comet ISON crosses into the northern sky. It should shine brighter than 1st magnitude and perhaps sport a spectacular tail. Northern Hemisphere viewers will get increasingly better views as Christmas approaches.
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Comet ISON reaches perihelion (closest to the Sun) November 28 and perigee (closest to Earth) December 26. // Astronomy: Richard Talcott and Roen Kelly
Using images acquired over the past two months, astronomers have made
initial estimates of Comet ISON’s water and dust production and used
them to infer the size of its icy nucleus.
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The Comet ISON imaging campaign is expected to yield infrared data and light curves, which are used in defining the comet’s rotation rate, in addition to visible-light images.
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John Chumack shoots the comet in January as it glows dimly at magnitude 16. Check it out »
Check out the January 2013 issue of Astronomy for a complete rundown of what might be the comet of the century. Buy it today »
Two astronomers, Vitali Nevski from Vitebsk, Belarus, and Artyom Novichonok from Kondopoga, Russia, discovered the comet on images they obtained September 21. In late 2013, Comet C/2012 S1 (ISON) probably will become the brightest comet anyone alive has ever seen. Learn more »