An image of Comet 46P/Wirtanen taken by Abel De Burgos Sierra from La Palma, in the Canary Islands, Spain, on 6 December 2018.
The comet nucleus is at the core of the brightest spot at the centre of the image, and the green diffuse cloud is its coma. The green colour is caused by molecules – mainly CN (cyanogen) and C2 (diatomic carbon) – that are ionised by sunlight as the comet approaches the Sun.
The comet reached perihelion, the closest point to the Sun along its orbit, on Wednesday 12 December, and is on the way to its closest approach to Earth this weekend, when it might become visible to the naked eye from dark locations.
A bright comet with a period of 5.5 years, 46P had been chosen in the 1990s as the target of ESA’s Rosetta mission. However, a launch delay prompted the mission team to select a new target, Comet 67P/Churyumov–Gerasimenko, which was visited by Rosetta between 2014 and 2016.
This image is a composite of three 10 second exposures using R, G, B filters on a Teleskop Service 130 f/5.7, using an Atik 460EX-M CCD. The field of view spans 58 arcmin x 46 arcmin.
Full story: December comet brings back Rosetta memories