“The Christmas comet”, 46P/Wirtanen

Comet 46P/Wirtanen is seen in this southern hemisphere telescopic view on Nov. 7, 2018. Image credit: Alex Cherney / NASA

Comets are very capricious stars, and if we wanted to compare them to a pet it would certainly be with cats, which always expect to be worshipped as “Gods”.

These days the “comet of Christmas” is trending. Just open google and type the word “comet” and in your first results you will find the 46P / Wirtanen. Its name comes from the surname of its discoverer Carl Wirtanen, whereas the letter P identifies it as periodic, as it has an orbital period of under 200 years. The last perihelion was reached in 2013 while the next one will happen in 2024, but what interests us at the moment is that on December 12th it will pass closest to the Sun, following with the point of maximum proximity to our planet set for December 16th.

On November 10th, Wirtanen made people talk about it, going from a visual magnitude of 11 to 8, reaching magnitude 6 towards the end of the same month. Currently its magnitude is 5.5 (therefore being visible to the naked eye from dark skies) and it is expected to reach magnitude 3.

Going back to the cats comparison: many times comets have been announced as spectacular and ended up in fiascos (see Kohoutek), so better go cautious, even though pleasant surprises are not excluded given their ice composition and that as they approach the Sun they are subject to outburst.

We just have to wait and in the meantime observe (these evenings it is between Eridanus and Cetus), even better with a pair of binoculars (I have observed it with a 8 × 42), or try to photograph it with a reflex and a simple 18 – 55. Below is a map to trace the position of the comet.

Andrea Cuozzo

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