Comet Lovejoy’s colourful coma

Newbury Astro member, David Boyd, recorded this spectrum of Comet C/2014 Q2 Lovejoy on 6th January 2015. The spectrum has been artificially coloured, and above it is the spectral profile showing the intensity of light emitted at each wavelength across the spectrum.


The spectrum tells us about the chemical composition of the comet. Molecules sublimating from the nucleus of the comet as it approaches the Sun emit light at very specific wavelengths characteristic of the individual molecules. The resulting emission lines appear as sharp spikes in the spectrum and the strength of the spikes tell us how much of each kind of molecule is present in the comet’s nucleus. Some of these lines have been labelled with the chemical names of their parent molecules. The spikes at around 4700 and 5100 angstroms show the presence of diatomic carbon (C2) which, with along with the spike labeled CN (cyanogen), are responsible for the comet’s green colour.


To capture the spectrum David used a LISA spectrograph, from the French company Shelyak Instruments, fitted with a Starlight Xpress SXVR-H694 CCD camera attached to a Celestron C11 scope. The spectrum is composed of twenty-two 5 minute exposures starting at 20.40UT and finishing at 22.30UT, guided continuously on the rapidly moving comet nucleus. The image below has been processed to bring out the structure in the comet’s tail.


Comet Lovejoy is currently travelling in a north-westerly direction through the constellation of Taurus and is sufficiently bright to be easily visible in binoculars, and possibly with the unaided eye from a suitably dark site. Charts showing its path over the next few weeks can be found at - then click on “comets-charts” in the menu on the left.

All images courtesy of David Boyd - 11 January 2015