If you miss Comet 46P/Wirtanen this year, it probably won’t be your last chance to see it. The blazing celestial body passes near the Earth roughly every five and a half years. But just because you can miss Comet 46P/Wirtanen doesn’t mean you should—because this year’s appearance promises to be one of the best in four centuries. And if that’s not enough, it’ll probably also be the brightest comet visible in 2018. Comets are at their brightest when they reach their perihelion, or closest approach to the sun. For Comet 46P/Wirtanen, this will fall on Sunday (Dec. 16).
Given all of that, you should still think carefully before hauling yourself out of bed. This smallish flying ball of dust, seven million miles away, is competing with a full moon and a busy night sky, as well as all the normal manmade noise. All this suggests it may not be visible with the naked eye—or it might just look like a greenish glow, far, far away. The most optimistic projections have it at magnitude 3, just slightly brighter than the dimmest star in the Big Dipper. Others suggest its magnitude might be just 7.6—and not visible with the naked eye. (The system is high-to-low, if you’re scratching your head over these numbers.)
If you want to take your chances or have a telescope on hand, the comet should be visible almost everywhere on Earth, bar its most southerly portions. Handy maps help show where it’ll be night by night. Stargazers, get your binoculars ready—though the rest of us may need to brace for an anticlimax.