Comet C/2012 S1 (ISON) is racing toward an uncomfortably close rendezvous with the Sun, according to a new series of images from the Gemini Earth Observatory. Comet ISON might present a stunning sight in the twilight sky of late November that will remain easily visible, even brilliant, into early December.
Gemini’s time-sequence images span from early February through May 2013, showing the comet’s remarkable activity despite its vast distances from the Sun and Earth. Data accumulated from the image series provides vital clues as to the comet’s overall behavior and the potential to present a spectacular show this fall. What scientists don’t know is if Comet ISON will survive its close brush with the Sun to become the early morning spectacle in late 2013.
During the image collection, the comet ranged between roughly 455-360 million miles (or 4.9-3.9 astronomical units) from the Sun. This put it just inside the orbital distance of Jupiter. The images, taken with the Gemini Multi-Object Spectrograph at the Gemini North telescope on Mauna Kea, Hawaii, reveal the comet in the far red part of the optical spectrum. This emphasizes the comet’s dusty material already escaping from what the astronomers call a “dirty snowball.”
The comet sports a well-defined parabolic hood in the sunward direction that tapers into a short and stubby tail pointing away from the Sun. Such features form when dust and gas escape from the comet’s icy nucleus and surround the main body to form a relatively extensive atmosphere called a coma. The coma’s material is pushed away from the Sun by solar wind and radiation pressure to form the comet’s tail.
