ESA’s space missions are getting ready to observe an icy visitor to the inner Solar System: Comet ISON, which might also be visible in the night sky later this year as a naked eye object.

The comet was discovered in images taken on 21 September 2012 by astronomers Artyom Novichonok and Vitali Nevski using a 40 cm-diameter telescope that is part of the International Scientific Optical Network, ISON.

Originating from the Oort Cloud, a repository of icy bodies billions of kilometres from the Sun, ISON is on a path that will bring it within grazing distance – 1.2 million kilometres – above the Sun’s visible surface on 28 November.

The NASA/ESA Hubble Space Telescope took detailed images earlier this year, such as the main image presented here from 30 April. In this composition, the comet is set against a separately imaged background of stars and galaxies.

For some time the view of the comet from Earth was temporarily blocked by the Sun, but it was spotted again in August, by amateur astronomer Bruce Gary.

Astronomers around the world are now eagerly watching as the comet draws closer, its coma – the tenuous atmosphere that surrounds the comet’s rock–ice nucleus – becoming more pronounced as its surface ices are heated by the Sun and transformed into gas. Dusty debris is suspended in the coma and swept into a tail, which will also become more prominent as the comet approaches the Sun.