Comet ISON shows plenty of promise as it nears Mars
BY KEITH COOPER
Posted: 26 September 2013
This great new image from British astrophotographer Damian Peach, who will be appearing at the Astronomy Now Comet Conference in London on 20 October, shows Comet C/2012 S1 ISON continuing to race towards the Sun. The glow of the comet's diffuse coma and growing tail are clearly visible as Comet ISON moves through the star-fields on the border between the constellations Cancer and Leo. Still 330 million kilometres from Earth, there remain strong hopes that ISON will eventually blossom to be as bright as Venus, or even brighter, when it approaches perihelion (its closest point to the Sun) on 28 November.
Currently the comet is at magnitude +11, which is far too faint to be seen with the unaided eye. Small telescopes should however provide a good view, with the comet coming well within range of binoculars by the beginning of November and, if all goes well, further brightening to be visible without optical aid by mid-November.
Before then, ISON has a close encounter with Mars on 1 October, coming within ten million kilometres of the red planet, which should provide a spectacular imaging opportunity for astrophotographers. NASA and ESA's fleet of robotic Mars orbiters will also take time away from Mars to study the comet. Reaching Mars will be a crucial time for Comet ISON – having crossed inside the 'snow line' in the Solar System that marks the point where water vapour freezes out, temperatures should begin to rise enough for water-ice to begin sublimating from the comet's surface and really bulk out its tail. By studying this behaviour astronomers will be able to get a better gauge on how spectacular ISON may become.