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May 2006 Feature: Jupiter rules the Night!


You just can't miss the planet Jupiter during May. This month, our planet Earth comes closest to Jupiter for the entire year, and Jupiter, in turn, blazes most brightly in our sky, outshining the night's brightest stars by leaps and bounds. This planet reigns as the third brightest celestial body of nighttime, after the Moon and the planet Venus.
Venus, however, can only be seen at morning dawn, whereas our feature attraction lights up the sky from dusk till dawn. On May 4, Earth in its orbit swings between the Sun and Jupiter, an event that's called an opposition of Jupiter. At this time Jupiter stands opposite the Sun in our sky, so it rises in the east at sunset and sets in the west at sunrise. Jupiter not only beams at its brilliant best for the year, but stays out all night long!
Jupiter shines in front of the rather dim constellation Libra the Scales. Because it's a constellation of the zodiac, the Sun, Moon and planets pass within Libra's borders periodically. Nowadays, the Sun resides in front of Libra from about October 31 (Halloween) till November 22.
The Scales, however, are a remnant from a bygone age. Several thousand years ago, the Sun stood in front this constellation on the autumn equinox -- one of the two days of the year when day and night are in the balance. The autumn equinox occurs annually on or near September 23, the Sun now passing through the constellation Virgo on this date.
On a dark, clear night, a rather faint yet visible star appears quite close to Jupiter. This is Libra's alpha star, named Zubenelgenubi. If you can't see this star with the eye alone, by all means try binoculars. Jupiter and Zubenelgenubi occupy the same binocular field all through May. What's more, binoculars reveal Zubenelgenubi to be a double star. Astronomers believe this double might be a true binary: two gravitationally-bound stars orbiting a shared center of mass.
If you could only see the stars at daytime, you'd see the Sun and Zubenelgenubi in conjunction on November 7.

copyright 2006 by Bruce McClure


April 2006 Feature * June 2006 Feature


Further information. . .
Rise/Set Times for Jupiter in the US and Canada
Rise/Set Times for Jupiter around the world
Jupiter through a telescope
Jupiter by Bill Arnett
Jupiter by Chuck Ayoub
Jupiter by Calvin J. Hamilton
Dates of Sun's Passage in Zodiacal Constellations