Observers in Western Europe looking to the south around 11pm local time on Sunday 7 May have a treat in store. If skies are clear you can see the 12-day-old waxing gibbous Moon pass little more than a degree north of largest planet Jupiter in the constellation of Virgo. For observers in the heart of the British Isles, this beautiful conjunction occurs 33 degrees (about one and a half spans of an outstretched hand at arm’s length) above the southern horizon when the pair are highest in the sky.
Now a month past opposition, magnitude -2.4 Jupiter is still a commanding presence as darkness falls, the brightest object in the evening sky aside from the Moon. The planet’s angular size just exceeds 43 arcseconds, meaning that a telescope magnification of just 42× is sufficient to enlarge it to the same apparent size as the adjacent Moon appears to the unaided eye.If you possess a quality 3-inch (7.6-cm) aperture telescope or larger capable of magnifying 100× or more, Jupiter displays not only its four Galilean moons — Io, Europa, Ganymede and Callisto — on 7 May, but also the planet’s Great Red Spot (GRS).
The GRS transits — that is, it crosses an imaginary line joining Jupiter’s north and south poles — at 10:42pm BST (21:42 UT). Jupiter’s rapid rotation soon carries the Great Red Spot away from the planet’s meridian, but it remains on show until about midnight as seen from the UK.
Visibility predictions for Jupiter’s Great Red Spot and Galilean moons may also be obtained via our interactive Almanac. To see the events for any given day, ensure that the ‘Add phenomena of Jupiter?’ checkbox is ticked. Like the GRS predictions, all Galilean moon phenomena are in Universal Time (UT), so add one hour for current UK events. For help using the Almanac, see this article.