10 january 2022

Bright comet Leonard does the show in the southern sky



While the comet Leonard (C/2021 A1) was approaching its perihelion on January 3 and was visible to the naked eye in the Southern hemisphere, the TRAPPIST-South telescope captured this magnificient image of the comet colorful atmosphere and tail.

Comets are icy planetesimals of the solar system whose ices sublimates when they get closer to the Sun. Their atmospheres, called coma, are made of gaseous species and also dust particules which are pushed away by the solar wind and radiation respectively, making the famous ion and dust tails. The blue color of the ion tail is dominated by recombining carbon monoxide molecules, while the green color of the head of the comet is created by the light emitted by diatomic carbon molecules. A very large deep blue halo is also visible and is made of cyanogen molecules. The Sun is to the right of the image.

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