Jovian moon events
WHEN: Throughout March as specified
Jupiter is well positioned for viewing this month, providing some interesting and unusual opportunities close to and around the planet’s disc. On 1 March it appears close to two 11th-magnitude stars, mag. +11.7 TYC 4965-932-1 and mag. +11.1 TYC 4965-61-1. On the 2nd you can witness a transit of Ganymede and its shadow, beginning at 22:39 UT and concluding at 01:10 UT on 3 March; Ganymede itself transits between 02:06 UT and 04:02 UT. On 4 March, the outer Galilean moon Callisto appears close to Jupiter’s northern limb at 22:00 UT.
A less favourable Ganymede plus shadow transit occurs on the morning of 10 March. The shadow transits between 02:37 UT and 05:06 UT, but the dawn twilight is well underway as Ganymede begins its crossing at 05:30 UT, moving off disc after sunrise at 07:26 UT, as Jupiter is setting.
The waning gibbous Moon (94% lit) rises in close proximity to Jupiter at around 20:30 UT on 14 March. They
remain close into the early hours of 15 March, enhanced by the presence of mag. +1.0 Spica (Alpha (_) Virginis) 5º to the south. Viewing Jupiter through a scope at this time should reveal mag. +10.8 star TYC 4964-1346-1 to the west of the planet, though it may look like an additional faint moon. The star is 2 arcminutes east of Jupiter (and close to Europa and Io) at 21:30 UT.
Another stellar encounter occurs on the morning and evening of 25 March when mag. +11.8 GSC 4964-597 appears close to the planet. See if you can spot the faint star 8 arcseconds north of Ganymede at 03:30 UT on 25 March.
There’s a good Io plus shadow transit on the morning of 27 March. Io’s shadow transit begins at 02:38 BST (01:38 UT), the moon’s transit at 02:55 BST (01:55 UT). The shadow passes off disc at 04:49 BST (03:49 UT) with Io following at 05:05 BST (04:05 UT). Later that evening, Io and Ganymede experience a double eclipse-occultation event. At 23:46 BST (22:46 UT), Io is eclipsed by Jupiter’s shadow. Ganymede follows suit at 01:39 BST (00:39 UT) on the 28th. Both moons then reappear from occultation behind Jupiter’s east limb; Io at 02:13 BST (01:13 UT), Ganymede at 04:54 BST (03:54 UT) during twilight.
As darkness falls on 29 March, two mag. +9.8 stars (TYC 4964-178-1 and TYC 4964-299-1) appear close to Jupiter’s disc, above and below the orbital plane of the four Galilean moons. On the morning and evening of 31 March, Jupiter encounters mag. +9.8, TYC 4964-379-1 in line with the moons. All four moons are brighter than mag. +6.0; the star will be identifiable because it’ll appear much dimmer.