Illustration by @VirtualAstro

A Bright Comet in the Sky

Comet 246P/Wirtanen: December 2018 is packed full of objects and events for the casual stargazer. Comet 46P/Wirtanen being another one of them this month.

Read on to find out more about this fabulous object and how to see it in December’s night sky.

What is a Comet?

In contrast to popular belief, they do not streak across the sky. Comets can take months to move across the heavens. Meteors streak across the sky lasting a brief moment to a few seconds.

Similarly, comets and meteors contain dust and rock. Comets are much larger than meteoroids comprising of ice as well as dust and rock. Regularly referred to as Dirty Snowballs.

Because of the dust and ice contained within, comets sublimate and release gas and dust forming diffuse tails.

Their tails usually point away from the sun due to the direction of the solar wind. The trails of dust left behind create some of our annual meteor showers like the Geminids.

You can read more about the different kinds of “Space Rocks” in a new article coming soon.

46P/Wirtanen

Discovered by Carl Wirtanen at the Lick Observatory in California in 1948. It’s a short period comet with an orbital period of 5.4 years.

46P/Wirtanen is relatively small, being just over a kilometre in size.

It is very active and releases more water vapour than other comets similar in size. This should hopefully provide quite a show as it gets closer to the sun (perihelion) mid December.

On December 16 it will be at Cometary Perihelion – its closest point to the sun. At the same time 46P/Wirtanen will also be at its closest point to earth just over 7 million miles away!

Therefore, if we keep our fingers crossed and combine it’s perihelion, proximity to Earth and volatile nature. We should be in for quite a show!

How and When to See it

Comet 46P/Wirtanen will reach naked eye visibility in December 2018. Maximum brightness expected on the evening of December 16.

The approximate brightness of the nucleus is expected to be magnitude 3. With a coma over an area the size of the full Moon. Because of this, it will be on the edge of naked eye visibility. However, it will be a stunning object in binoculars or a telescope.

Where to see 46P/Wirtanen

Pleiades and 46P/Wirtanen December 16 2018
Illustration by @VirtualAstro and Stellarium

At the start of December 2018 46P/Wirtanen will be in the southern sky in the constellation of Cetus the Sea Monster.

It will then get higher in the sky moving into the constellation of Taurus the Bull.

At Perihelion on December 16, it will be very close to the Pleiades and expected brightest at this time.

The comet will then travel northeastwards to the constellation of Auriga the Charioteer and lessen in brightness as the month moves on. It will finally make its way into Ursa Major in January and no longer be easily spotted.