A family portrait
WHEN: 3, 5 and 12 June at the specified times
Jupiter’s largest and brightest moons, the Galilean satellites, can be easily seen through a small telescope. The quartet appear to pass back and forth either side of Jupiter, with only outer Callisto able to miss the planet’s disc when tilt conditions are right.
The other three sometimes pass in front of, and sometimes behind, Jupiter’s disc. On 5 June, between 21:48 and 23:49 BST (20:48 and 22:49 UT), there’s a chance to see the shadows cast by Io and Europa both crossing the disc at the same time. A similar situation occurs on the night of 12/13 June, with both Io and Europa’s shadows crossing Jupiter between 00:26 and 02:50 BST (23:26 and 01:50 UT).
Earlier in the month, on the 3rd, there is a surprisingly uncommon opportunity to catch two moons close and west of the planet with the other two close to the east. This almost perfect family portrait is further enhanced by the Great Red Spot being centrally positioned. There is a catch though, as this arrangement occurs at 20:05 BST (19:05 UT), while the Sun is still up. From the UK, the best opportunity occurs at 22:20 BST (21:20 UT) in a darker twilight sky, when you should just catch Ganymede before it starts to transit.
Jupiter’s perfect portrait can be seen at 20:05 BST (top) though the sky may be too bright; if that’s the case, wait for darker skies (bottom)