Comet C/2012 S1 or Ison
Comet Ison is a sungrazing comet. It is known as C/2012 S1 among astronomers.
The comet was discovered on 21 September 2012 by Vitali Nevski of Belarus and Artyom Novichonok of Russia. The discovery was made using the 40cm (16 inch) reflector telescope of the International Scientific Optical Network near Kislovodsk, Russia and the automated asteroid-discovery program CoLiTec. After its discovery, the comet was also found from images taken in earlier dates like images by the Mount Lemmon Survey from 28 December 2011 and by Pan-STARRS from 28 January 2012. To confirm the discovery, follow-up observations were made using the iTelescope network on 22 September by a team from Remanzacco Observatory in Italy. The discovery was announced by the Minor Planet Center on 24 September 2012. After its discoverers, the comet is also known as Comet Nevski-Novichonok.
Observations by SWIFT satellite suggest that C/2012 S1's nucleus is around 5 km (3.1 mile) in diameter.