NIGHT WATCH

Su­per moon in the bull’s horns

go! - - Upfront In Brief -

n 4 De­cem­ber, the day af­ter full moon, the moon will reach “perigee” – the point on its or­bit clos­est to earth. The closer the moon, the big­ger it seems. The full moon in De­cem­ber will be the “big­gest” of the year. But there’s more. On 3 De­cem­ber, look for a bright, red star close to the moon. This star is called Alde­baran and it’s the eye of Tau­rus the bull. ( The con­stel­la­tion is an up­side down V – the bull’s “horns” point down­ward be­cause we’re in the south­ern hemi­sphere.) Many peo­ple call the perigee moon a “su­per moon” and warn that it might cause nat­u­ral dis­as­ters. Fake news. Re­mem­ber, the moon comes this close to the earth ev­ery month with­out do­ing any dam­age, the only dif­fer­ence is that it’s not al­ways full. The moon’s or­bit is el­lip­ti­cal and the dis­tance from earth varies from about 357 000 kilo­me­tres to 406 000 kilo­me­tres – about a 14 % dif­fer­ence in ap­par­ent size. Take a photo of the su­per moon in De­cem­ber and re­peat the ex­er­cise for the mini moon on 26 Au­gust 2018. Use iden­ti­cal cam­era set­tings and com­pare the pho­tos to see the dif­fer­ence in size. The full moon looks even big­ger when it rises and sets be­cause of the so-called “moon il­lu­sion” – an op­ti­cal il­lu­sion that causes the moon (or sun) to ap­par­ently in­crease in size near the hori­zon. The rea­son for the il­lu­sion is not fully un­der­stood. – Wil­lie Koorts

Alde­baran

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