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![]() When is the last time something rang clear and true in your life and you made immediate changes? What resulted?
January 29, 2008: Wake up before dawn on an arctic-cold February morning .... and go outside? This Friday you'll be glad you did. The two brightest planets in the Solar System, Venus and Jupiter, are converging for a spectacular close encounter. The best time to look: Friday morning, February 1st. Venus and Jupiter will be so close together, you can hide them behind the tip of your index finger held at arm's length: sky map. You'll need a clear view of the southeastern horizon to see the show. Venus and Jupiter will be hanging low, like landing airplanes, easily hidden behind tall buildings or trees. So go out beforehand (at noon when it is warmer) and find a gap to look through so you won't have to hunt for one in the dark on Friday. It's worth the effort because Venus and Jupiter will be less than 1o apart, like twin headlights piercing the rosy glow of sunrise. It's a beautiful scene. In fact, you may not be able to take your eyes off of it. Venus and Jupiter are literally spellbinding. There is a physiological basis for this phenomenon. When two planets appear so close together, they grab an extra share of your brain's attention. Consider the following: "Your eye is like a digital camera," explains Dr. Stuart Hiroyasu, O.D., of Bishop, California. "There's a lens in front to focus the light, and a photo-array behind the lens to capture the image. The photo-array in your eye is called the retina. It's made of rods and cones, the fleshy organic equivalent of electronic pixels."
Near the center of the retina lies the fovea, a patch of tissue 1.5 millimeters wide where cones are extra-densely packed. "Whatever you see with the fovea, you see in high-definition," he says. The fovea is critical to reading, driving, watching television. The fovea has the brain's attention. The field of view of the fovea is only about five degrees wide. On Friday morning, Venus and Jupiter will fit together inside that narrow angle, signaling to the brain, "this is worth watching!" If you can tear your eyes off Venus and Jupiter, glance to the right: Another close encounter is underway. The crescent Moon appears directly beside the red giant star Antares. With only 2o between them, the Moon and Antares will fit inside your fovea as well. Friday morning should not be missed, but if you do miss it, don't worry, the show continues as February unfolds. Venus and Jupiter will remain relatively close together for several days to come while the Moon moves in to join them. Mornings of note include Sunday, Feb. 3rd, when the Moon, Venus and Jupiter arrange themselves in a slightly-bent line, and Monday, Feb. 4th, when the trio form one of the most exquisite celestial triangles you'll ever see.
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"It's the Geminid meteor shower," says NASA astronomer Bill Cooke of the Marshall Space Flight Center. "Start watching on Thursday evening, Dec. 13th, around 10 pm local time," he advises. "At first you might not see very many meteors—but be patient. The show really heats up after midnight and by dawn on Friday, Dec. 14th, there could be dozens of bright meteors per hour streaking across the sky." Right: A Geminid meteor in 2006 photographed by Christopher Colley of Lombard, Illinois. [Larger image] The Geminids are not ordinary meteors. While most meteor showers come from comets, Geminids come from an asteroid—a near-Earth object named 3200 Phaethon. "It's very strange," says Cooke. How does an asteroid make a meteor shower? Comets do it by evaporating. When a comet flies close to the sun, intense heat vaporizes the comet’s "dirty ice" resulting in high-speed jets of comet dust that spew into interplanetary space. When a speck of this comet dust hits Earth's atmosphere traveling ~100,000 mph, it disintegrates in a bright flash of light—a meteor! Asteroids, on the other hand, don't normally spew dust into space—and therein lies the mystery. Where did Phaethon's meteoroids come from?
Cooke favors another possibility: "I think 3200 Phaethon used to be a comet." Exhibit #1 in favor of this idea is Phaethon's orbit: it is highly elliptical, like the orbit of a typical comet, and brings Phaethon extremely close to the sun, twice as close as Mercury itself. Every 1.4 years, Phaethon swoops through the inner solar system where repeated blasts of solar heat could easily reduce a flamboyant comet to the rocky skeleton we see today. If this scenario is correct, Phaethon-the-comet may have produced many rich streams of dust that spent hundreds or thousands of years drifting toward Earth until the first Geminid meteors appeared during the US Civil War. Since then, Geminids have been a regular shower peaking every year in mid-December.
3200 Phaethon is now catalogued as a "PHA"—a potentially hazardous asteroid whose path misses Earth's orbit by only 2 million miles. It measures 5 km wide, about half the size of the asteroid or comet that wiped out the dinosaurs 65 million years ago, and can be seen through backyard telescopes—in fact, now is a good time to look: "3200 Phaethon is flying past Earth just a few days before this year’s Geminid meteor shower," notes Cooke. On Dec. 10th, Phaethon will be about 11 million miles away shining like a 14th magnitude star in the constellation Virgo: ephemeris. That's too dim for the naked eye, he says, but a good target for amateur telescopes equipped with CCD cameras. Cooke doesn't expect the flyby to boost the Geminids—"11 million miles is too distant to affect meteor rates"—but the Geminids don't really need boosting. "It's always a great shower," he says. "Don't miss it." |