Look­ing back: The Sky at Night

May 1986

Sky at Night Magazine - - INSIDE THE SKY AT NIGHT -

On the 25 May 1986 episode of The Sky

at Night, Pa­trick Moore looked at the lat­est re­sults from the Giotto space­craft, which few past Hal­ley’s Comet on 14 March that year.

The comet or­bits around the Sun once ev­ery 75 years, and in 1986 it passed through the in­ner So­lar Sys­tem – the frst such close ap­proach since the start of the space race. To take ad­van­tage, an ar­mada of fve space­craft was launched to ex­plore the comet, in­clud­ing ESA’s Giotto.

The space­craft passed just 1,373km from the comet nu­cleus. At this dis­tance, it was bom­barded by dust from the comet, and one large im­pact sent the space­craft spin­ning just 7.6 sec­onds be­fore clos­est ap­proach. Thank­fully, Giotto re­cov­ered, and was able to take the frst close-up images of a comet nu­cleus, re­veal­ing the comet as peanut shaped and roughly 15km in length.

Giotto an­a­lysed the com­po­si­tion of Hal­ley’s Comet, fnd­ing it was largely the same as the so­lar neb­ula. This im­plied it was a prim­i­tive body that had re­mained rel­a­tively un­changed since the be­gin­ning of the So­lar Sys­tem.

Giotto (in­set) un­locked mys­ter­ies about the size and shape of Hal­ley’s Comet

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