Sky Talk March 2012: Night Sky’s Six Brightest Objects at Once!

As March opens, skywatchers will be treated to the rare opportunity of seeing Mercury, Venus, Jupiter, Sirius, the Moon and Mars all above the horizon at the same time after sunset. And while each of these objects is itself a wonderful telescopic sight, this event is best enjoyed using the unaided eye alone to sweep across this celestial panorama.

Stepping outdoors about 30 to 45 minutes after sunset the first three evenings this month, an amazing display of the sky’s six brightest objects will be found spread out from the southwestern horizon to the eastern one. Lowest in the west is the shy and elusive planet Mercury (which may require your Edmund binoculars to be well seen, depending on how bright the twilight sky is at the time you look). It’s followed higher up (and eastward) by dazzling Venus — which, as the third brightest object in the entire heavens after the Sun and Moon, can’t possibly be missed! Higher yet is Jupiter (which, as described below, will come very close to Venus at mid-month). Next is the brilliant blue-white star Sirius in the south, brightest of all the stars in the heavens. Roughly above it will be the gibbous Moon and, finally, further to its east fiery Mars. Wow — what a spectacular celestial lineup this will be!

As the month progresses, Mercury will quickly drop lower in the west and disappear into the sunset while the Moon will continue its never-ending eastward journey around the sky. Interestingly, although Mercury will have been lost to sight, Saturn rises in the east later in the evening to take its place — still leaving six of the sky’s luminaries above the horizon at the same time! But there’s more happening this month, involving the two brightest of the planets. Keeping an eye on Venus and Jupiter from night-to-night, you’ll notice the two worlds drawing closer together. On the evenings of March 12th and 13th, they will be just 3 degrees apart, both easily fitting into the field of view of any binocular. And here telescope owners will want to examine each of these objects separately, just 25x being enough magnification to show their dissimilar disks (and Jupiter’s four bright Galilean satellites).

While the two planets appear close together in the sky at this time, in reality they are quite far apart in space — Venus being about 75,000,000 miles from us and Jupiter 525,000,000. (But compared to Sirius, they are right in our backyard. Among the closest stars, it lies over 50 trillion miles from our Solar System!) These lovely worlds afterward slowly separate, ending up some 15 degrees apart by the end of March and with Venus moving higher in the sky on its way to a spectacular conjunction next month with the famed Pleiades Star Cluster (be sure to check out the April Sky Talk about this event).

— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of eight books on stargazing.


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