"The surface of the Earth is the shore of the cosmic ocean... Recently, we've managed to wade a little way out, and the water seems inviting." - Carl Sagan
Preparing for comet ISON
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.
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.
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.
The comet will be brightest in our skies just before and in the week after its encounter with the Sun, assuming it survives, but will likely have faded by the time it makes its closest approach to Earth on 26 December. It will pass Earth with no threat of impact.
Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)