Hello everyone, and welcome to “Ask The Beak,” a new segment where we answer questions from fans who think, for whatever reason, that we’re the right sort of people to clear things up. This week’s question comes from long-time reader and occasional contributor Princess Wolfsbane:

“Heard anything more interesting about the green comet than just this summary? I’m not sure what else there is to find out about it at this stage, but if there is more, I would be interested in reading about it in The Beak.”
–Princess Wolfsbane, Brooklyn, NY (Via e-mail)

Well Princess, let’s start out with what we know from the provided Discovery Channel link. The comet’s name is Lulin, and was discovered by a Chinese undergrad in 2007. It’s currently visible in North America, and expected to reach its closest (and therefore most visible) point relative to the Earth on February 24. And it’s green, which, presumably, is what our questioner is really interested in. Regarding the greenness, Discovery says,

“The color is caused by gases spewing off the comet nucleus as it heats up during its trip toward the sun. The gases glow green in sunlight.”

…Which is a bit vague. Comets are composed primarily of water-ice and rock, with various gases mixed in. As with most other objects in the universe, a body’s color depends on its chemical composition. NASA, thankfully, has seen fit to fill in the blanks:

“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.”

So I’d say that’s pretty interesting, dear reader. The comet is poison! A fucking poisonous comet! Is this a great solar system or what? Not that Lulin’s supply of cyanogen (which, here on Earth, is generated from cyanide compounds) is going to have any effect on us. Though, again according to NASA’s write-up, we wouldn’t have known this a century ago:

“In 1910, many people panicked when astronomers revealed Earth would pass through the cyanogen-rich tail of Comet Halley. False alarm: The wispy tail of the comet couldn’t penetrate Earth’s dense atmosphere; even it if had penetrated, there wasn’t enough cyanogen to cause real trouble. Comet Lulin will cause even less trouble than Halley did. At closest approach in late February, Lulin will stop 38 million miles short of Earth, utterly harmless.”

Summary: Lulin is green because it’s full of poison gas, but too far away to poison us here on Earth. It’s also probably too far away to be seen in brightly-lit areas like New York City (where this week’s letter-writer lives), but in case any of you are planning on being out in the styx in the next few weeks, Sky and Telescope has some tips on the best times to look.

If you would like a Beakly perspective on a lingering issue that’s been bothering you, write to lordhoratio(AT)gmail(DOT)com and varius(AT)thebeak(DOT)org and maybe we’ll answer your question on a slow news day.