S&T News Bulletin - Dec 30



Thanks to last summer's comet impacts, Jupiter sports a new dark belt in
its southern hemisphere, the second-most obvious one on the planet after
the South Equatorial Belt.  Astronomers using the 3.5-meter reflector on
Calar Alto report that a continuous *bright* band can be seen in that
latitude range at the infrared wavelength of 1.7 microns. This means that
debris ejected upward remains suspended high in the atmosphere.  Now a
team of European astronomers report that the band is significantly dimmer
-- and thus cooler -- than its surroundings in the thermal infrared at 7.8
and 7.9 microns.  These wavelengths are sensitive to the presence of
methane in Jupiter's middle stratosphere. The team suggests either that
the stratosphere now contains gases like water, ammonia, and hydrogen
cyanide which efficiently radiate energy to space, or that a high-altitude
haze above the impact zone is reflecting enough sunlight to keep the gases
below relatively cool.

Jupiter currently rises more than two hours before the Sun, sitting above
the horizon in the southeast to the lower-left of brilliant Venus.  It
will continue to move away from the Sun at nearly 1 degree per day.  By
mid-January the elongation will exceed 45 degrees, making Jupiter once
again observable by the Hubble Space Telescope.


S&T Contributing Editor John Bortle urges you to track down Periodic Comet
Borrelly, which he says is an unusual and impressive object.  The comet is
about magnitude 8.5, making it easy to spot with modest telescopes or even
good binoculars.  But through a larger telescope P/Borrelly displays *two*
faint tails, pointing toward and away from the Sun at position angles of
265 and 115 degrees.  "It looks a bit like a skewed, edge-on galaxy,"
Bortle says, and he adds that P/Borrelly hasn't sported an antitail since
its apparition in 1918. The comet reached perihelion on November 1st and
is now drifting slowly across the western stars of Ursa Major.  As 1995
begins you'll find it just barely west of the 3.8-magnitude star Nu Ursae
Majoris.  Here are upcoming positions for 0 hours Universal Time:

         R.A. (2000) Dec.
Jan 1   9h 50m   +59.2 deg
    3   9  51    +60.3
    5   9  52    +61.3


New Moon falls on New Year's Day, and Robert C. Victor notes that
observers in southwestern states and Hawaii have the opportunity to spot
the very thin crescent of a very old Moon on the previous morning,
Saturday, December 31st. On the East Coast the crescent will then be 23
hours from new, 20 hours in the west, and 18 from Hawaii.  Look to the
southeast about 45 minutes before sunrise.

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   | Stuart Goldman         Internet: sgoldman@cfa.harvard.edu  |
   * Associate Editor                 mrastro@aol.com           *
   | Sky & Telescope                                            |
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