|Comet C/2006 M4 (SWAN)|
This comet emerged from behind the Sun in September 2006. Having arrived
straight from the Oort cloud, Comet SWAN is making its first visit to the
inner solar system. Due to its hyperbolic orbit it is set to leave into
outer space and never to return.
The name SWAN stands for Solar Wind ANisotropy experiment, which is carried aboard the SOHO spacecraft.
Light polluted London skies and field rotation prevented a longer exposure
time - which would have revealed a significant comet tail. As many other
comets, Comet SWAN is exhibiting a green glow; this is due to the cyanogen
(CN) and diatomic carbon (C2) contained in the comet's coma - these
substances glow green when illuminated by sunlight.