23 January 2015

Comet Lovejoy photographed near Tabuk – Record by Viv Wilson

Comet Lovejoy is a gassy comet with a short tail appearing green proably due to the presence of two gases – cyanogen (CN)2 and diatomic carbon (C2) – which glow green when their molecules are ionised. Ionisation causes electrons within the molecules to gain energy and when the electrons drop back down to their normal state, they give off light of a certain wavelength. For these molecules they emit green light and since they are very strong emitters, their green colour dominates the comet.  The evening sky remains free of moonlight for excellent views until about January 23rd or 24th, when the waxing Moon will brighten the sky further each night. Lovejoy passed closest by Earth on January 7th, at a distance of 70 million kilometers. Although the comet is now receding from us, its intrinsic brightness is still increasing slightly. That's because it doesn't reach its closest to the Sun, until January 30th although by this date the comet will be fading from Earth's point of view and the Moon will be brightening. The comet covers 3° per day at its peak, meaning it will move noticeably in a single observing session. Amateur astronomer Terry Lovejoy discovered this object on August 17, 2014, from Brisbane, Australia. Comets that first light up the deep southern sky tend to have orbits inclined steeply to the solar system’s plane, a characteristic that often carries them well north after they wheel around the Sun. The below photographs were taken 16 January 2015, in the desert near to Tabuk in north-west Saudi Arabia by Viv Wilson who has kindly allowed me to use them on my website.