Star Points for November, 1997; by Curtis Roelle
Forecast: Increasing Chance of Meteor Storm?

     The changing weather of November reminds us winter cannot be
postponed much longer.  The warm days of Indian Summer are
retreating, chased off by cold wind and rain as trees, formerly
dressed in radiant autumn foliage, turn skeletal.  Through a
celestial cycle of earthly seasons the days enjoy fewer hours of
sunlight.  The intensity of the light being received pales in
comparison to the more direct rays when the Sun stood high in the
sky at local noon on summer days. 

     The cycling calendar is also bringing around another season of
holiday gift giving.  Perhaps you are thinking of purchasing a
telescope or binoculars for a young scientist (or at least young-
at-heart)?  I suggest that you attend the free Holiday Telescope
Buyers Workshop sponsored by the Westminster Astronomical Society
of Maryland (WAS).  A number of telescopes owned by members will be
on display for your inspection.  Information on optical design,
practical use, pricing, and manufacturers will be available to help
with your buying decision.  If you already own a telescope, bring
it in for a free tune-up.  Members will be on hand to answer
questions about your existing instrument to make your telescoping
experience as rewarding as possible.  The workshop is Wednesday
November 12 at the Bear Branch Nature Center from 7:30 to 9:30 p.m. 
Call 410-549-3150 between 7 and 9 p.m. for more information.

     You may be pleased to know that a telescope is not required to
enjoy one of November's annual astronomical spectacles: the Leonid
meteor shower.  This year the shower is predicted to peak after
midnight on the evening of November 16-17.

     The Leonids have a long history.  On November 16, 1966 meteor
observers were astonished by a sudden outburst of meteors described
as a "meteor storm".  So many meteors were seen that their number
was difficult to measure.  Some described the effect as driving
into a blizzard as meteors estimated at rates of up to several
hundred thousand meteors per hour appeared to emanate from a point,
or "radiant", in the constellation Leo.  This event was not
unexpected as dramatic displays of the Leonid meteor shower had
been recorded throughout history.  The Arabs dubbed 902 A.D. as
"the year of the stars."  From 1799 onward the Leonid storms were
observed every 33 years.  However in 1933 nothing happened, so the
expected reappearance in 1966 was not a certainty.  

     A number of accounts and illustrations by eyewitness to
earlier Leonid storms is given in Carl Sagan's book "Comets"
(Random House, 1985).  Here is an account of the 1866 Leonids
recounted by Robert Ball:

     "The night was fine; the moon was absent.  The meteors
     were distinguished not only by their enormous multitude
     but by their intrinsic magnificence.  I shall never
     forget that night...All the tracks of the meteors
     radiated from Leo...Occasionally luminous trains would
     linger on for many minutes after the meteor had flashed
     across, but the great majority of the trains in this
     shower were evanescent.  It would be impossible to say
     how many thousands of meteors were seen, each one of
     which was bright enough to have elicited a note of
     admiration on any ordinary night." -- Robert Ball, 1900

     The next Leonid outburst is predicted to occur in 1998 or
1999.  This year should also be favorable because the shower has
been improving steadily.  Last year WAS members observing from
various locations in Maryland and West Virginia noticed an
encouraging increase in the number of particularly bright meteors
associated with the shower.  The meteors were observed to leave
lasting contrail-like "trains" whose ghostly glow persisted even
after the meteor had vanished.  Unfortunately moonlight is expected
to interfere with the Leonid display this year.  

     What are meteors and where do they come from?  While meteors
have other names such as "falling stars" or "shooting stars" they
are not stars at all.  Stars are much too far away to exhibit the
rapid motion witnessed for meteors which streak swiftly across the
sky in Earth's upper atmosphere.  Each Leonid meteor is a grain of
cosmic dust traveling through space as a "meteoroid" that glows
briefly as it collides with the Earth's protective atmosphere.  As
they enter the atmosphere traveling at 40 miles per second friction
in the upper atmosphere causes them to burn up more than 50 miles
high.  Our atmosphere acts as a shield, protecting us as we enjoy
the show from a safe distance.

The material that makes up the stream of meteoroid material was
given off by the comet 55P/Tempel-Tuttle which was first observed
in 1366.  The comet, which takes 33 years to circle the Sun, will
be faintly visible in shiny new telescopes come January.  This
appearance of the shower's parent comet heralds the coming of the
next predicted Leonid storm.

The best time to observe the Leonids this year is on the night of
Sunday, November 16-17.  Earth crosses the plane of the comet's
orbit between midnight and dawn -- a good thing for observers in
Maryland.  As dawn approaches Leo rises high in the sky so more
meteors will be above our horizon. 

Dress warm and get comfortable.  A sleeping bag and a reclining
lawn chair is one way.  You want to be able to have a clear view of
the sky free from surrounding buildings and trees.  The bright
moonlight should not prevent the brightest Leonids from being
viewed, but it will probably wash out the glowing trains left in
their wake.