A possible naked-eye comet
WHEN: All month, best mid-month when the Moon’s out of the way
DURING DECEMBER, COMET C/2013 US10 Catalina finally starts to become easier to see for those of us located in the UK. And the good news is that C/2013 US10 Catalina should be a naked-eye comet. It’s expected to be around the mag. +5.0 mark, as it climbs higher in our morning sky at the start of December. It’ll be close to the 4th-magnitude star Kappa Virginis, but will slowly crawl northward, through Virgo and into Boötes. At the end of the month, the comet will be very close to bright orange Arcturus (Alpha (_) Boötis), and this will provide an easy way to locate it.
The Moon will be in its waning phases at the start of December, approaching the region containing the comet as a 15%-lit crescent on the morning of the 7th. Even though this will be a very thin phase for the Moon, its light can still interfere with the view of a delicate extended target such as the head and tail of a comet.
Talking of bright things, the brilliant dot of Venus will be close by at the start of December too. Both comet and planet appear to sidestep one another during the early part of the month. Closest approach will be around 7 December, when they will be a little under 4º apart.
The Moon is new on 11 December as the comet continues to climb higher in the morning sky. A higher altitude will make C/2013 US10 Catalina easier to see, aided by it reaching its brightest magnitude around this period, possibly up to mag. +4.0.
The best tool to spot the comet will be a pair of binoculars. However, once you’ve located it, don’t forget to look at the same region with just your eyes to see if you can see that rare astronomical sight – a naked-eye comet.