Ison

ISON, officially designated C/2012 S1 (ISON), was a long-period comet discovered on 21 September 2012 by Vitali Nevski and Artyom Novichonok at the International Scientific Optical Network (ISON) near Kislovodsk, Russia. The discovery by the ISON collaboration drew attention to the possibility that the object could become one of the brightest comets visible from Earth in late 2013.

It was on a highly elongated, nearly parabolic orbit with a predicted perihelion distance of about 0.012 astronomical units from the Sun, scheduled for 28 November 2013. As it approached the Sun, observers anticipated a spectacular display, potentially visible even in daylight.

However, in the weeks leading up to perihelion, the nucleus underwent fragmentation and loss of material. By October 2013, the comet’s nucleus had not been detected; by the time of perihelion, observers reported only faint debris, and no active nucleus or coma remained.

The ISON event is cited as a notable example of a sungrazing comet whose interior structure and response to solar heating determined its fate. It also highlighted uncertainties in predicting comet brightness and the challenges of observing a fragile body near the Sun. The discovery underscores the role of the ISON network in coordinating observations of small bodies in the Solar System.