The Plan­ets

Sky at Night Magazine - - CONTENTS -

Jupiter is at op­po­si­tion on 9 May, a time when the planet is in the op­po­site part of the sky to the Sun. This means that May is an ex­cel­lent month to ob­serve Jupiter. On 9 May, Jupiter shines at mag. –2.4 and presents a disc that ap­pears 44 arc­sec­onds across. At this ap­par­ent size there is plenty of de­tail up for grabs through the eye­piece of a tele­scope. A small scope will clearly show the planet’s oblate shape, the re­sult of its rapid ro­ta­tion. In ad­di­tion, its two main belts are eas­ily seen ei­ther side of the Jo­vian equa­tor.

The Great Red Spot is one of the ob­serv­ing high­lights on Jupiter and can be seen through a tele­scope with a 100mm or greater aper­ture. The spot rep­re­sents a per­sis­tent storm in Jupiter’s at­mos­phere. The Jo­vian at­mos­phere is very dy­namic. For ex­am­ple, ear­lier this year, a storm out­break in the south tem­per­ate belt (STB) was ob­served.

The four largest moons of Jupiter – Io, Europa, Ganymede and Cal­listo – are also fas­ci­nat­ing to watch. As they pass be­tween Jupiter and the Sun they cast vast shad­ows on the at­mos­phere be­low, which can be seen with rel­a­tively small tele­scopes. Be­fore op­po­si­tion it’s in­ter­est­ing to watch how the moons chase their shad­ows, catch­ing up with them on op­po­si­tion day and then lead­ing them af­ter op­po­si­tion. There are a num­ber of such events vis­i­ble this month (see pages 50, 51 and 52 for more in­for­ma­tion), which spec­tac­u­larly il­lus­trate the ef­fect. From the UK, Jupiter is now sadly los­ing alti­tude as it heads east to­wards a more southerly part of the eclip­tic. Its max­i­mum height from the cen­tre of the UK is around 21°. By the end of the month, Jupiter will have nudged west enough to sit within a de­gree of Zubenel­genubi (Al­pha (_ Li­brae).

Jupiter will reach op­po­si­tion in Libra on 9 May and will be high­est in the sky around 01:00 BST

De­spite its fame, the Great Red Spot is sur­pris­ingly tricky to spot with smaller scopes

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