Brightest comet of 2018 to whizz past Earth just in time for Christmas

10 Dec 2018

Comet 46P/Wirtanen will appear more like a fuzzy ball rather than one with a tail. Image: © fabio lamanna/

Coming as an early Christmas present to stargazers, Comet 46P/Wirtanen will be one of the closest flybys of its kind in decades.

While everyone will be pretty busy in the run-up to Christmas, you might want to set aside some time later this week to stare into the night sky to see a once-in-a-lifetime sight.

According to, Comet 46P/Wirtanen – named after the astronomer Carl Wirtanen, who discovered it in 1948 – will whizz closely past Earth at a distance of 11.5m km from our planet at 1.06pm UTC on 16 December. This makes it the among the closest comet approaches to Earth since 1950, and can even be included among the 20 or so closest since dating began in the ninth century AD.

Comet 46P is a member of the so-called ‘Jupiter family’ of comets, of which more than 400 are known. They have relatively short orbital periods of 20 years or less, with Jupiter as their farthest point.

Since it was first discovered, the comet has been observed almost every year, but is tricky to spot due to its orbit resulting in it being faint, even with large telescopes. However, this is all about to change thanks to its close approach to Earth, with astronomers predicting that it will be visible to the naked eye, and even more impressive using a telescope or binoculars.

A slight disappointment

In fact, while it will make its closest approach on 16 December, astronomers predict it should be visible without aids around 13 December, with it remaining visible in the northern hemisphere until early January.

However, those expecting to see a dazzling display are likely to feel a bit disappointed, as its small size – approximately 1.1km in diameter – makes it one of the smallest cometary nuclei found to date. To put this into perspective, Comet 46P is only one-thirtieth the size of the famous Comet Hale-Bopp.

On top of that, Comet 46P won’t have much of a tail – if there is one at all – as its size means it will likely only produce a faint gas. Instead, it will probably look more like a fuzzy ball of light, which could prove very difficult to see in a light-polluted sky.

Don’t let this fool you into thinking that it won’t be worth checking out, however, as its next orbit of Jupiter – and the ones that follow – will push the comet farther from Earth during its flyby. Therefore, this will be the closest it will come to us in hundreds – if not thousands – of years.

Colm Gorey was a senior journalist with Silicon Republic