Comet 46P/Wirtanen brightens
WHEN: 6-18 October when Moon interference is lowest
South-moving comets seem to be the theme this month. While 21P/Giacobini-Zinner travels down the eastern side of Canis Major, 46P/Wirtanen moves south into the constellation of Fornax, the Furnace.
However, unlike 21P, comet 46P is brightening. Don’t be fooled by its apparent poor positioning and direction. The comet continues to head south through October and into the start of November, but as we head through the main part of November it turns northeast, rapidly accelerating and brightening as it goes.
Consequently, if you can find it this month then you’ll be well-prepared to observe it at its best later in the year, when Wirtanen is predicted to become a naked-eye comet. Spotting it now means you’ll be ready for the transition and have a head start on those who only start trying to locate it when it brightens up.
It begins the month 5° south and slightly east of mag. +4.0 Upsilon (p) Ceti. Despite its very low UK position, its motion south is quite slow during October. It’ll be 1° west of mag. +5.4 Pi (/) Fornacis on the night of 13/14 October and by the end of the month will have tracked approximately 6° south of where it was on 1 October.
Wirtanen begins October at mag. +9.7 but is expected to have brightened to +8.7 by the time it passes Pi Fornacis. By the end of the month, the comet is predicted to be at mag. +7.4; an overall brightening of 2.3 magnitudes throughout October.
The region of sky Wirtanen will be travelling through is best seen when at its highest position in the sky, due south. This occurs at 02:30 BST (01:30 UT) on 1 October, 01:30 BST (00:30 UT) on 15 October and 23:30 UT at the end of the month. Good luck with your comet hunt but if you don’t find it, don’t despair. Comet 46P/Wirtanen is just about to start the main show!