Comet 46P/Wirtanen is 2018’s brightest comet and comes closest to Earth on December 15–16, 2018—this weekend! As awesome as they can be, you can’t trust comets. We can always predict where they’ll be, but not how they will react with the Sun’s energy. So, the question is: Will it be an amazing sight or another bust?
For a short background, Comet 46P/Wirtanen is indeed the brightest comet in the night sky, though it’s been too faint to see with the naked eye thus far. From dark sky sites, however, it could just become naked-eye visible soon as it comes closest to Earth on its 5.4-year-long looping orbit.
We’ve had a goodly number of busts, such as comet Ison a few years ago that was touted as “The comet of the Century” but never got bright at all.
On the other hand, we’ve had two spectacular comets since the mid-70s—the pre-dawn mind-blower Comet West in March of 1976, and then Hale Bopp, which remained brilliant for almost an entire year, mostly in 1997.
We’ve also had a bunch of visible-but-not-brilliant comets in the form of Comet Kohoutek in 1973, Comet Iras-Iraki-Alcock in 1983, Halley in the autumn of 1985, and Hyakutake in 1996. The new one is comet Wirtanen.
How to See Comet 46P/Wirtanen
This is a good news / bad news kind of deal.
The bad is that it’s an unusually tiny comet whose nucleus is just 1/2 mile wide.
The good news is that on December 15 and 16 it will pay Earth its closest-ever visit. It’ll pass just seven million miles from us. I’ve been watching it through binoculars the past few nights, and think it will brighten to be visible to the naked eye for those in rural regions. It’s doubtful whether it will become bright enough to appear in the glowing skies over cities, although you never know. It should be large and blobby looking, appearing as a fuzzy glob the size of the full Moon.
Comet Viewing Tips
The comet isn’t going to be super bright like a star. Each night, it’s slowly moving. Still, it’s rewarding to spot the comet’s passage.
My suggestion is to look halfway up the southern sky starting around 10 p.m. beginning tonight or the next clear night (away from city lights and light pollution).
Face east, shortly after nightfall.
Look for Orion, one of the most recognizable constellations in the sky. See the three bright stars that make up the belt?
Now sweep your binoculars upwards from Orion to the famous Seven Sisters star cluster, also known as the Pleiades. If you don’t already know the Pleiades, this is a good time to make their acquaintance. At 10 p.m. any night, look south and you’ll easily see a small, tightly packed group of stars. That’s it. The six naked-eye stars in the cluster will gloriously multiply to dozens, and their blue-white diamond color will be obvious too. It’s the very best celestial target for binoculars.
Now look just below the Pleiades star cluster (more to the lower right).
During the comet’s closest pass, it will be just below the Pleiades star cluster. The comet will be brightest on the nights of Saturday, December 15 and Sunday, December 16.
Here’s a helpful sky map showing the location of the comet. Image credit goes to earthsky.org.
If the weather isn’t clear, there will be a live viewing of the comet the evening of December 16. Check out the Virtual Telescope for more information.