Jovian moon and shadow transits
WHEN: Throughout the month at the times specified
An eyepiece view ( south is up) of some of the exciting moon and moon-shadow transits visible during March
JUPITER IS A wonderful planet to look at through a telescope because its disc is large enough to show some tantalising atmospheric detail. Another highlight is the quartet of Galilean moons – Io, Europa, Ganymede and Callisto – which constantly dance around Jupiter’s globe.
Lying more-or-less in Jupiter’s equatorial plane, from Earth we get to see some interesting interactions between these moons and the planet. One of the most impressive is the passage of a moon and its shadow across the cloud tops of Jupiter below. This month there are a number of these events worth looking out for.
Right at the start of the month on 1 March, it will be possible to see the shadow cast by the outermost Galilean moon, Callisto. The transit of this shadow will be visible between 03:02 UT and 06:22 UT, with the moon itself transiting the northern portion of Jupiter between 05:11 UT and 07:28 UT.
There’s a lovely double transit involving the moons Io and Europa on 8 March, the date Jupiter reaches opposition. At this point, the shadows cast by the moons will be in line with their respective discs, appearing slightly south of them. Both moons and shadows will be fully in transit between 00:31- 01:54 UT.
On 9 March as the sky is darkening and Jupiter rising, you should be able to spot the shadow of the giant moon Ganymede in transit. As Ganymede slips off the limb at 18:57 UT, Io and its shadow
will be starting their transit on the opposite side. Ganymede’s shadow will have fully left the disc by 19:14 UT.
There are a couple of noteworthy events starting on 15 March, with Io and Europa once again involved in a double transit. Both moons and both shadows will be on disc from 02:20 UT to 04:10 UT. Another double event occurs on the night of 16 March, when between 20:51 UT and 22:09 UT, Io, Ganymede and their shadows will be fully on Jupiter’s disc. It will be interesting to compare the sizes of Io’s shadow with that of giant Ganymede.
On 17 March Callisto can be seen in transit between 19:15 UT and 21:45 UT. Its shadow follows suit, crossing Jupiter’s disc between 21:02 UT and 00:14 UT on 18 March. The shadow appears almost as Callisto has reached the other side of Jupiter.
Two further impressive double transits can be seen: on 22 March starting at 04:24 UT between Io and Europa; and from 23:51 UT on 23 March until 00:34 UT