Show up ISON! You have got the green light! The latest images of ISON show the 'Comet of the Century' shining green! October 8 2013This stunner was captured by Adam Block on Ocotober 8 2013, just before sunrise, atop Mount Lemmon. This beautiful image features ISON's greenish coma, trailed by a long, straight tail.
© Adam Block
Comet ISON is green in the sky atop Mount Lemmon, Arizona on October 8 2013
© Michael Jäger
Green Comet ISON on Oct. 5, 2013 in the sky over Weissenkirchen, Austria.

ISON's green color comes from the gases surrounding its icy nucleus. Jets spewing from the comet's core probably contain cyanogen (CN: a poisonous gas found in many comets) and diatomic carbon (C2). Both substances glow green when illuminated by sunlight in the near-vacuum of space.

The comet is zooming within the orbit of Mars, heading toward a crucial rendezvous with the sun on Nov. 28. Get your telescope ready!