Comet 46P/Wirtanen

Comet 46P/Wirtanen, 15 Dec 2018 6:54:21 – 6:59:21 UT, Dodgeville, WI (Photo by David Oesper)

Carl A. Wirtenen (1910-1990) was born in Kenosha, Wisconsin and nearly 71 years ago he discovered a comet on a photographic plate while doing a stellar proper motion survey at the Lick Observatory in California.

Comet 46P/Wirtanen orbits the Sun once every 5.44 years at a distance ranging from 1.06 AU at perihelion to 5.13 AU at aphelion.

Carl Wirtanen discovered five comets, but 46P/Wirtanen is the only one that is not a long-period comet. The others are C/1947 O1, C/1948 N1, C/1948 T1, and C/1956 F1-A.

Comet 46P/Wirtanen reached perihelion on Wednesday, December 12 at 4:38 p.m. CST, and made its closest approach to the Earth since its discovery (7.2 million miles) on Sunday, December 16 at 7:05 a.m. CST. It will not pass this close to Earth again until sometime after the year 2197.

The photo above was taken just 30 hours before Comet 46P/ Wirtanen made its closest approach to Earth. I used a digital SLR camera with 300mm telephoto lens piggybacked on the telescope I use for asteroid occultations. I was able to manually guide on the comet’s nucleus which was easily visible as a “fuzzy” star using a sensitive video camera imaging through the telescope. Comet 46P/Wirtanen’s nucleus is estimated to have diameter of just 3,900 ft., and it rotates once every 8.9 hours.

In the three-image sequence below you can definitely see the comet’s motion relative to the background stars.

Comet 46P/Wirtanen, 15 Dec 2018 6:38:17-6:41:18, 6:45:23 – 6:49:24, and 6:54:21 – 6:59:21 UT

How do you pronounce “Wirtanen”? See here.