Asteroid Herculina should be an easy spot in Orion and Taurus this month
Asteroid 532 Herculina reaches opposition on 2 December when it will brighten to mag. +10.1 as it moves from Orion into Taurus, where it spends most of December. As the weeks pass, it only dims by 0.3, ending the month at mag. +10.4. The good news is that it is particularly easy to identify and gets to a good altitude under the darkness of a winter sky, giving you a great opportunity to track this relatively dim object over the month.
Herculina was discovered in April 1904 by Max Wolf at the Heidelberg-Königstuhl State Observatory. Wolf was a pioneer of astrophotography and had developed photographic methods to automate the discovery of asteroids. Wolf himself discovered an impressive 248 asteroids in his lifetime.
Herculina is a large main belt asteroid estimated to be 200km across. Its precise shape and size are still to be confirmed, but it is believed to be like a battered cube, a shape some have described as resembling a toaster! Its orbit takes it out as far as 3.26 AU and in as close as 2.29 AU from the Sun, taking 4.62 years to complete. At favourable oppositions, Herculina shines at mag. +8.8, while at unfavourable ones, it dims down to mag. +12.0.
During December, Herculina can be found travelling between mag. +3.2 Pi3(π 3) Orionis in a gentle arc taking it west-northwest towards mag. +4.3 Mu (μ) Tauri. This path is less than 10° to the south of the V-shaped Hyades open cluster, presenting an opportunity to record the cluster and asteroid in a single photograph. Overlaying and ‘blinking’ a series of photographs will show the movement of 532 Herculina, as well as several other asteroids in the vicinity.