Wednesday, November 08, 2006

Mercury Transit

Jaidee Children's Fund
Mercury passes by sun on Wednesday

The picture shows Mercury's passage in front of the sun to be seen in U.S. by EST.( Photo)

The picture shows Mercury's passage in
front of the sun to be seen in U.S. by EST.(
Photo Gallery

Nov. 7 (Xinhua) -- On Wednesday, Nov. 8, the planet Mercury will pass directly
in front the sun. The transit begins at 2:12 p.m. EST (19:12 GMT) and lasts for
almost five hours, according to NASA's forecast.

    Good views can be had from the Americas, Hawaii,
Australia and all along the Pacific Rim. During the transit, Mercury's tiny
disk-- jet black and perfectly round -- will glide slowly across the face of the
sun. Only a speck of the sun's surface is actually covered, so the sun remains
as dangerous as ever to look at. But with a proper filter and a little
imagination, the transit of Mercury can be a marvelous experience.

    There are many ways to safely observe the sun, e.g.,
through eclipse glasses or by means of a pinhole projector. In this case,
nothing beats a telescope equipped with a sun-safe H-alpha filter. H-alpha
filters are narrowly tuned to the red glow of solar hydrogen.

    Mercury is fantastically mysterious. More than half
of the planet is unknown to us. When Mariner 10 flew by in the mid-70s, it
managed to photograph only 45 percent of Mercury's cratered surface. What lies
on the other side? More craters? Or something totally unexpected? We're free to
speculate, because the next spacecraft to visit Mercury, NASA's MESSENGER probe,
won't enter orbit until 2011.

    One of Mercury's greatest secrets is the
mystery-material at its poles. Radars on Earth have pinged Mercury and received
a strong echo from polar craters. A favorite explanation is ice. While Mercury's
daylight surface heats up to 400 degrees Celsius, the temperature in deep, dark
polar craters dips below -200 degrees Celsius. If an icy comet landed in one of
those craters (or made one of those craters), the comet's ices, vaporized by
impact, might re-freeze and stick around. As skeptics like to say,however, "it's
just a theory," one of many that MESSENGER will check.

    Another puzzle is Mercury's wrinkles. Geologists call
them "lobate scarps." Like wrinkles on a raisin, the scarps are thought to be a
sign of shrinkage. Mercury may actually be collapsing in on itself as its
massive iron core cools and contracts. To check this idea, MESSENGER will map
Mercury's magnetic field, which springs from the core. If the core is
collapsing, the collapse may leave telltale signs in the planet's magnetism.
MESSENGER will also look for lobate scarps on the uncharted side of Mercury to
see if this is truly a global phenomenon.

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