Meteor shower post..Check this out..Huh? What was that guy's name?<g>
Heading out soon..can't miss deal
Stunning Leonid shower expected
By THOMAS J. MORGAN
Journal Staff Writer
Tonight planet Earth will slash through the tail of Comet Tempel-Tuttle,
an encounter that some astronomers have calculated might produce one
of the blockbuster meteor storms of recorded history, ranging from
Europe to North America.
Thirty-three years ago, up to 150,000 meteors per hour filled the sky
with glinting shafts of light. A meteor shower known as the Leonids
weighs in every year at this time. But historical accounts traced back as
far as the 10th century show that brilliant Leonid meteor outbursts often
replace the ordinary variety in 33-year cycles, the time it takes
Tempel-Tuttle to complete one orbit of the sun.
The Leonids' 33-year peak in 1999 could be the last for anyone alive
today. According to Sky & Telescope magazine, the planet Jupiter will
deflect Tempel-Tuttle in 2029, three years before its next visit, and the
comet's intense meteor storms may not return until 2098 or 2131.
That would be a nostalgic farewell, for the great Leonid meteor storms in
1833 and 1899 provided clues that enabled astronomers to figure out
finally that comets were the source of meteors. In fact, according to
comet forecaster Joe Rao of Sky & Telescope, material cast off by
Tempel-Tuttle as it blazed past the sun exactly a century ago is what lies
ahead tonight.
Like litterbugs, comets toss out trash in the form of dust and pebbles as
they hurtle through space. This rubble whirls along in the same orbit as its
parent, forming a river of rocks, dust and ice particles. The stuff gradually
spreads out along the orbit, but is more concentrated in the vicinity of the
comet.
Tempel-Tuttle whipped around the sun early last year, and this part of its
wake -- discarded in 1899 and still rocketing along roughly 600 days
behind the comet -- is reckoned by astronomers to be prime meteor real
estate.
Starting around midnight, people living along the East Coast will find out
whether that assessment is correct.
On the other hand, tonight's show might prove to be a bust, because
forecasting meteor showers is like juggling an oiled eel.
''The beauty is if you're right you're famous, if wrong forgotten,'' said
Peter H. Schultz, a planetary astronomer who is director of the Northeast
Regional Planetary Data Center at Brown University.
Schultz is hedging his bets.
''This is the year that everybody had predicted would be the peak -- 33
years after 1966,'' he said. ''But everything depends on where the
clumpiness is, where the greatest concentration of debris might be.''
David Targan, an astronomer and associate dean at Brown University,
was equally cautious.
''This year was predicted to be the best,'' he said. ''Some astronomers
have calculated that the rate of meteors could be as high as tens of
thousands per hour. But first of all, who knows?''
Amateur astronomer David A. Huestis of the Skyscrapers Club in
Scituate, who will conduct a ''meteor tour'' for the Audubon Society of
Rhode Island at its reserve in Coventry, had these thoughts: ''Some
predictions indicate the eastern U.S. might be favored for a tremendous
show. Other predictions aren't so kind. All I can say is we must be
prepared for anything.''
The dust and pebbles are invisible to us while in space. So no one can be
certain where the peak fall of debris, which could last only an hour, will
occur as the Earth rotates eastward.
''It could occur in the middle of the ocean, and no one would see it,''
Targan said. ''On the other hand, it could occur right overhead, over the
eastern part of the United States.''
Then again, the Leonid meteor stream is broad, and an ordinary annual
encounter will produce a dozen or so meteors per hour. Targan said that
if the night is clear, ''people just casually looking at the night sky for 15
minutes or so will see meteors. No question about it -- probably even
from downtown Providence.''
The meteor shower was named the Leonids because the meteors appear
to radiate from the constellation Leo. The radiant, a C-shaped star group
in Leo known as the Sickle, does not rise above the eastern horizon until
around midnight. A clear view of the horizon is needed in order to see
anything at that point, but the radiant will rise high in the sky as the hours
pass.
A gibbous moon -- about three-quarters full -- may interfere with early
sightings, but it will set at 12:48 a.m.
And then there's the weather.
According to the National Weather Service, the sky will be partly cloudy
with clearing toward dawn. No rain is forecast.
What are comets?
''They are the closest thing to nothing that anything can be and still be
something,'' said Schultz.
A comet is a blob of ice and dust thought to be material left over from the
formation of the solar system. Billions of them are believed to orbit in a
cloud far beyond the orbit of Pluto, the farthest planet. Faint gravitational
tugs, sometimes from giant planets such as Jupiter, Saturn, Neptune or
Uranus -- or perhaps from nearby stars -- dislodge them, and they begin
a long journey inward to the sun.
As they approach the sun, solar radiation starts heating the comets,
causing jets of gas and steam to spew out in various directions. Carried
along with these outbursts are the dust and pebbles that eventually
become meteors. The small particles are jostled so that some precede
the comet while others fall behind.
''In 902 A.D. we find the first anecdotal account of the meteor shower,''
said Schultz. ''Chinese astronomers reported in the next century that
stars fell like rain. The year 902 fits into the 33-year cycle when you
allow for changes in the calendar. This comet got its name when two guys
named Ernest Tempel and Horace Tuttle independently discovered it in
1866.
''At that time they made the estimation that this was a link to the meteor
shower. They had already predicted the Leonid storm was going to
occur, but they had not linked it to the comet.''
If Tempel-Tuttle crosses Earth's orbit, could it one day collide with the
planet?
''It's like running across the freeway with one car coming along per hour.
The likelihood is very slim.'' What would happen if it hit Earth?
''My suspicion,'' said Schultz, who specializes in studying ancient impact
sites around the planet, ''is that it would form a crater maybe 10 or 15
kilometers -- it's not a very big comet -- I assume it's less than a
kilometer across at the nucleus -- but it's moving at 70 kilometers per
second.''
What would happen to the planet?
''This is one of the reasons we study them. We know that the Earth is in
harm's way. It's like target practice. We have these things whizzing by,
and we will be hit. The key is whether we get hit by a BB or by a
cannonball.
''Occasionally we get hit by a Mack truck.''
The planet was struck by a ''Mack truck'' about 65 million years ago, he
said. It gouged out a huge crater in the Yucatan Peninsula of Mexico,
traces of which can still be seen today. It is thought that the dust blown
into the air blacked out the whole planet and caused mass extinctions
worldwide. The dinosaurs may have met their doom this way, many
scientists believe.
Those worried about Tempel-Tuttle can relax, Schultz said.
''It's definitely not going to happen with that comet for a long, long time. |
