Comet Lovejoy

For the past few months, Comet Lovejoy (C/2014 Q2) has been visible in the night sky to binocular bearing observers or those with good eyesight and a dark night.  Recently discovered on August 17th 2014 by Terry Lovejoy, this comet has just made its approach near the sun as part of its ~8000 year orbital period.  I recently volunteered to be a part of the Harvard Observing Project (HOP) and spent some time in the Harvard Clay Telescope on top of the Science Center with Graduate Students John Lewis and Jane Huang.  Despite the usual Bostonian light pollution (and some spotlights from a Chris Pratt event), we managed to capture this image:

This image conveys an interesting phenomenon, comets actually glow green.  This green glow is due to the icy composition of the comet interacting with the solar wind.  The solar wind is a mess of charged particles that are given off by and orbit the sun at high speeds.  When these ions impact upon the the oxygen in the ice of the comet, the oxygen is briefly ionized and emits its characteristic green spectral lines.

A careful observer will note that the background stars are blurred.  This is because the telescope is tracking the comet, which moves relative to the celestial sphere.  With a 10-30 second exposure on the image, the slight movement of the comet again the background blurs the stars.

Sources:

Harvard Observing Project

http://en.wikipedia.org/wiki/C/2014_Q2_(Lovejoy)