Double Shadow Transit Season for the Jovian Moons Begins

New Horizons nabs a double shadow transit en route to Pluto. Image credit: NASA/JPL/New Horizons

Watching the inky-black shadow of a Jovian moon slide across the cloud-tops of Jupiter is an unforgettable sight. Two is always better than one, and as the largest planet in our solar system heads towards opposition on March 8th, so begins the first of two seasons of double shadow transits for 2016.With an orbit of 1.8 days, shadow transits of the innermost Galilean moon Io are by far the most common. The innermost three large moons of Jupiter (Io, Europa and Ganymede) are in a 1:2:4 resonance, meaning that double shadow transits involving Io and Europa and the most common. With an orbital period of 16.7 days, outermost Callisto is the only large moon of Jupiter that can occasionally ‘miss’ transiting the disk of Jove, owing to its slight 0.2 degree orbital inclination. The current ongoing season of Callisto transits wraps up this year on September 1st, and will not resume again until late 2019.Here’s a selection of favorable double shadow transit events this coming Spring for North America:February 26th (Io-Europa) from 9:39-10:01 UTMarch 4th (Io-Europa) from 11:32-12:38 UTMarch 8th (Io-Europa) 00:28-01:56 UTMarch 15th (Io-Europa) 2:21-4:34 UTMarch 22nd (Io-Europa) 4:23-7:10 UTMarch 29th (Io-Europa) 7:00-8:24 UTApril 5th (Io-Europa) 9:36-10:17 UTApril 12th (Io-Europa) 12:11-12:14 UTMay 7th (Io-Callisto) 4:38-5:44 UTYou can see a complete list of double shadow transits worldwide for 2016 here.The first good event of the series kicks off this week early on the morning of Friday, February 26th, and the series runs until May 7th. The second season of the year runs from August 7th to November 8th but is less than favorable, as Jupiter reaches solar conjunction on September 26th, and is hence near the Sun when the next series occurs. We combed through all mutual shadow transit events for 2016, and found 27 overall.<iframe —> Read More