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Wednesday, October 5, 2011

What's that bright object in the east early in the evening?

We have been getting alot of this question by phone and email from sky watchers. That very bright object in the east-northeast just after the end of twilight is Jupiter, now shinning at magnitude -2.8 in the constellation Aries. It is so bright now that you can become gobsmacked just looking at it from a dark sky. Jupiter will come to opposition on October 28th, when it will rise as the sun sets and be in the sky all night long. In a telescope Jupiter now presents the largest planetary disk of all the planets in the solar system, 48" of arc in diameter. This disk is, of course, to small to see with the naked eye, but it may be just visible in 10x binoculars. In a telescope it looks gigantic at high power.

If you have binoculars, be sure not to miss the 4 Galilean moons -- Io, Europa, Ganymede, and Callisto -- at least some of which are easy to spot in binoculars depending on their orbital location. You can watch their position change over the course of an hour, an example of a mini-solar system and gravity at work!

Jupiter, at center (over exposed), surrounded by the four Galilean satellites, named after their discoverer, Galileo Galelli.

And remember to "Keep on Looking up!"


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