Comet 46P/Wirtanen will be cruising by our planet later this month:
Ranked in terms of distance from Earth, this will be the 20th closest approach of a comet dating as far back as the ninth century A.D., and the tenth closest approach since 1950. The minimum distance between 46P and the Earth (perigee) will be 11,586,350 kilometers (7,199,427 miles), occurring December 16, 2018, at 13:06 Universal Time, a little less than four days after the comet passes its minimum distance from the Sun of 187 million kilometers (98.1 million miles).
Don’t expect a thrilling show. Despite its close approach, this one will probably not be another Hale-Bopp. It may reach 3rd magnitude, but even so it will likely be difficult to see if conditions aren’t excellent.1 And if you do find it, it probably won’t look like the popular image of a comet with a bright nucleus and tail, but instead will be a circular cloud in the sky a little brighter toward the center. The moon will be bright then, too, which won’t help.