May 1, 2006
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Look southeast after dark this month, and you'll see a bright white "star"
looking right back at you. This is the planet Jupiter, shining so brightly that you can't help but notice it even through city light pollution.
Jupiter blazes so bright mostly because it's a big planet, but also because on May 3rd it is at opposition: positioned opposite the Sun in our sky and at its nearest to Earth for the year. Jupiter will remain nearly as bright for the rest of May and throughout the coming summer, since it doesn't get much farther from us even several months after opposition. It will be the "star" of all the warm-weather nights in 2006.
Telescope users have been following a strange event brewing on Jupiter. Amid the planet's cloud belts, a long-enduring "white oval" unexpectedly turned reddish last February — matching the color of Jupiter's centuries-old Great Red Spot. Both amateur and professional astronomers have been tracking "Red Spot Junior."
Jupiter's spots are enormous cyclonic storms somewhat like hurricanes on Earth. White ones are topped by clouds of ammonia crystals in Jupiter's super-cold upper atmosphere. The reddish tints, planetary astronomers believe, arise from contaminant compounds of sulfur, phosphorus, or hydrocarbons welling up from inside Jupiter's mysterious, gaseous interior.
To see the Great Red Spot and "Red Spot Junior," you'll need a large amateur telescope with high-quality optics. Jupiter rotates once every 9 hours 56 minutes; a list of times when the Great Red Spot crosses Jupiter's centerline, as seen from Earth, appears in the May issue of Sky & Telescope magazine or can be generated online for any date at SkyandTelescope.com/redspot. "Red Spot Junior" follows behind about 1 hour 10 minutes after the Great Red Spot. Examples: on May 3rd, the Great Red Spot is centered at 10:35 p.m. Eastern Daylight Time; on the 12th, at 9:57 p.m. Pacific Daylight Time.
Two Crumbling Comets
Meanwhile, the May night sky offers two different illustrations of how comets in our solar system disintegrate and contribute to the supply of meteors — "shooting stars" — that you occasionally see zipping into Earth's upper atmosphere on a dark night.
1) High in the eastern sky in late evening, amateur astronomers are tracking pieces of Periodic Comet Schwassmann-Wachmann 3 (named for the two German astronomers who discovered it in 1930). It has been crumbling to pieces right before our eyes. The largest two chunks — or rather their gassy, glowing heads and tails — are dimly visible in amateur telescopes if you know exactly where to look. Much better views with the Hubble Space Telescope and the European Southern Observatory's Very Large Telescope in Chile show that several chunks of the disintegrating comet are breaking up even further. More information and sky charts are in the May Sky & Telescope and the May/June issue of Night Sky.
2) The annual Eta Aquarid meteor shower should be at its peak before dawn on May 5th. We see a meteor shower whenever Earth passes through a stream of old comet debris in space. The Eta Aquarid shower is visible mostly from the Southern Hemisphere and the tropics; very few of its meteors are visible from as far north as most of the United States. The Eta Aquarid shower is notable because it consists of debris shed long ago by the famous Halley's Comet, which will next return to our part of space in 2061.
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