Preliminary Analysis of SOHO/STEREO Observations of Sungrazing Comet ISON (C/2012 S1) Around Perihelion

Understand

We present photometric and morphological analysis of the behavior of sungrazing comet C/2012 S1 ISON in SOHO and STEREO images around its perihelion on 2013 November 28.779 UT.

• ISON brightened gradually November 20-26 with a superimposed outburst on November 21.3-23.5.
• The slope of brightening changed about November 26.7 and was significantly steeper in SOHO's orange and clear filter images until November 27.9 when it began to flatten out, reaching a peak about November 28.1 ($r_H{\sim}17 R_\odot$), then fading before brightening again from November 28.6 ($r_H{\sim}5 R_\odot$) until disappearing behind the occulting disc.
• ISON brightened continuously as it approached perihelion while visible in all other telescopes/filters.