Comet ISON

Astroimager Damian Peach from Hampshire, England, captured Comet ISON (C/2012 S1) on September 24, 2013, with a 17-inch corrected Dall-Kirkham reflector and an FLI PL-6303e CCD camera. He combined five 3-minute luminance images with 2-minute images through red, green, and blue filters.

Damian Peach

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.

As fall begins, Comet ISON is coming in range of medium-sized telescopes. 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.

Comet ISON reaches perihelion (closest to the Sun) November 28 and perigee (closest to Earth) December 26. // Astronomy: Richard Talcott and Roen Kelly

Observing Information

How to view Comet ISON in early October

Mars points the way to this celestial visitor as it brightens before dawn. Learn more »

Comet ISON captured September 24

Astroimager Damian Peach from Hampshire, England, captured the comet with his 17-inch corrected Dall-Kirkham reflector. See the gallery »

Comet ISON: The real story

Editor David J. Eicher responds to the naysayers and clarifies what we really know about how ISON will perform this fall. Watch now »

Catch Comet ISON with your camera

Be ready to photograph this special celestial visitor with these expert tips. Learn more »

Comet ISON captured September 16

After a month of trying, frequent contributor Chris Schur captured the comet through his 12.5-inch Newtonian reflector. See the gallery »

Easy-to-find objects in the 2013 autumn sky

As Senior Editor Michael E. Bakich explains in this video, Comet ISON will be a prime attraction as the temperatures drop. Watch now »

The Great Comet of 2013

This special issue gives you a front row seat for Comet ISON’s once-in-a-lifetime visit! You’ll find everything you need to know to experience what could be the brightest comet in decades at its best. Get it now »

An interview with comet ISON's co-discoverer

Artyom Novichonok answers questions about his interest in astronomy, his comet discoveries, and what it's like to find what could be the comet of the century. Learn more »

Hubble captures Comet ISON with stars and galaxies

Researchers with the Hubble Space Telescope released a new image of Comet ISON on July 25. This composite includes photographs taken through two filters. Learn more »

Hubble captures gas emission from Comet ISON

Images with Spitzer’s Infrared Array Camera indicate carbon dioxide is slowly and steadily “fizzing” away from the comet, along with dust. Learn more »

Hubble keeps an eye on Comet ISON

The Hubble Space Telescope captured Comet ISON on May 8 as the solar system interloper was 403 million miles (649 million kilometers) from Earth, between the orbits of Mars and Jupiter. See the time-lapse video »

April 27 — Efrain Morales Rivera

Frequent online contributor Efrain Morales Rivera shot Comet ISON as it traversed the constellation Gemini. See the gallery »

Hubble captrues Comet ISON

The comet, which the Hubble Space Telescope imaged April 10, is already active as sunlight warms the surface and causes frozen volatiles to sublimate. Learn more »

Swift sizes up Comet ISON

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. Learn more »

March 2 — Pat Knoll

Astroimager Pat Knoll created this image of Comet ISON by combining shots at the beginning and end of a session through the 22-inch William Kuhn Telescope at the Orange County Astronomers Observatory near the town of Anza, California. See the gallery »

February — Dean Salman

Arizona astroimager Dean Salman imaged Comet ISON and several galaxies through a 20-inch telescope from Kitt Peak National Observatory. See the galery »

Deep Impact spacecraft eyes Comet ISON

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. Learn more »

Is Comet ISON the comet of the century?

John Chumack shoots the comet in January as it glows dimly at magnitude 16. Check it out »

Will Comet ISON be a superstar?

Check out the January 2013 issue of Astronomy for a complete rundown of what might be the comet of the century. Buy it today »

Comet ISON will light up the sky

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 »