SCIART-L Archives

SciArt-L Discussion List-for Natural Science Illustration-


Options: Use Forum View

Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Frank Ippolito <[log in to unmask]>
Reply To:
SciArt-L Discussion List-for Natural Science Illustration- <[log in to unmask]>
Fri, 12 Nov 1999 09:57:52 -0500
text/plain (125 lines)
Hey Folks,

This just came through the museum pipeline. If things go as Mr Rao hopes,
it might be worth stepping outside during the evening hours next


Of the dozen or so meteor showers per year, this particular one
(called the "Leonids" and named for the constellation Leo from which
its shooting stars appear to emanate) would not normally be worthy of
comment except that its otherwise-unremarkable parent comet
Tempel-Tuttle was just in the neighborhood.

Comets are large balls of frozen, filthy ice. (Manhattan-size comets
are not unusual.) When they near the Sun's heat in their elongated
orbits they evaporate and lay a trail of detached dust particles
behind them.  If the comet's orbit happens to cross Earth's orbit (as
do the orbits of a dozen or so comets) then Earth plows through
thousands of tons of their debris at relative speeds of 20 to 50
miles per second.  The particles burn up in Earth's upper Atmosphere
as their energy of motion converts to heat, creating incandescent
streaks across the sky.

But the closer Earth comes to the actual location of the comet in
space the more significant the meteor shower is expected to be.
Comet Tempel-Tuttle was recently where Earth will be Wednesday night.
According to calculations performed by Hayden's own Joe Rao we have reason
to believe that this year's Leonid meteor shower -- better termed a meteor
"storm" -- will brings thousands of shooting stars per hour, compared
with its more tame annual average of 10 to 20 per hour.

The Middle East will be best positioned for this display since its
longitude lie on Earth's leading edge as we plow through the peak of
the debris stream, but many of us are hopeful that some debris will
be left over when the East Coast rotates into the path several hours

Many satellites in orbit around Earth will be taking precautionary
measures.  For example, the Hubble Space Telescope will be going into
"safe-mode" during the passage, where the mirror's shutter closes
down and the telescope orients so that its solar panels are parallel
to the meteor stream rather than broadside to it.

You needn't worry, however, as long as you don't go into orbit next week.

I enclose Joe Rao's predictions below.



If the weather cooperates and skies are clear that night, millions of
along the Eastern Seaboard of the United States may catch one of the best
meteor shower to occur in decades.

A regular mid-November event, the Leonid meteor shower, could be extra
good this year, perhaps even briefly attaining the status of a "meteor
with shooting stars visible to the naked eye every few seconds.  Such a
spectacle could develop as the Earth passes into a trail of dust-like
left behind by the comet Tempel-Tuttle (the comet itself swept by the
and Sun last year).

But no one knows exactly how good any given meteor shower will be, even
they expect the best.

The peak of the Leonids should come  sometime between 9:08 and 11:17 p.m.
Eastern Time on Wednesday night.  During that time frame, he notes,
the Earth will be sweeping within approximately  242,000 miles of
the center of a cloud of debris that was shed by comet Tempel-Tuttle
a century ago (in 1899).  If the meteor peak happens around
9:08 p.m., little or nothing of the expected meteor display would be seen
since by Americans because the constellation of Leo - from which
the meteors get their name - would still be below the horizon.
But Leo begins to rise soon after 11 p.m.; hence if the peak comes
later in the evening the odds would favor making quite a few meteor

 From Europe and North Africa, some predictions are suggesting anywhere
from many hundreds, to many thousands of meteors per hour, but nobody can
say with certainty just how many will be seen.

Prospective meteor observers on this side of the Atlantic should
carefully watch the sky, especially overhead and toward the northeast
beginning anytime after 10 p.m.  The farther you are from the haze or
pollution thrown off by big cities and towns, the better.

Use a tilt-back chair at a site with a clear view of the sky.  Let your
adjust to the darkness for about 15 minutes.  Lie back and gaze up at the
stars.  Every now and then a meteor will flit across the sky.  Faint ones
tiny, quick streaks.  Brighter ones may sail across the heavens for
seconds and leave a long-lasting glowing trail.  By dawn on Thursday
- if you care to stay out that late - the constellation Leo will have
high up toward the southern part of the sky.  By lying on your back, you
see meteors occasionally shooting out of that area like spokes of a wheel.

The Leonids move around the Sun in a direction opposite to that of the
  Hence, they crash into our atmosphere head-on at speeds of up to 45
per second.  They appear to the eye as darts or streaks of light.
they can appear to silently explode in mid-flight, creating brighter
of light.  Just the sight of one of these types of meteors will make the
evening worthwhile.

You just might need to see a few more metoers just to offset typically
November  temperatures. Bundle-up! It's always best to watch a meteor
with a companion -- shower with a friend!