February 2, 2013 – GREEN COMET LEMMON – 2013 could be the Year of the Comet. Comet Pan-STARRS is set to become a naked eye object in March, followed by possibly-Great Comet ISON in November. Now we must add to that list green Comet Lemmon (C/2012 F6). “Comet Lemmon is putting on a great show for us down in the southern hemisphere,” reports John Drummond, who sent us a picture from Gisborne, New Zealand: “I took the picture on Jan. 23rd using a 41 cm (16 in) Meade reflector,” says Drummond.
“It is a stack of twenty 1 minute exposures.” That much time was required for a good view of the comet’s approximately 7th-magnitude coma
(“coma”=cloud of gas surrounding the comet’s nucleus). Lemmon’s green color comes from the gases that make up its coma. Jets spewing from the comet’s nucleus 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.
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