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(meteorobs) Cockermouth AS Leonids Info Sheet
Hi List,
Lew asked me to post this... hope some non-experts find it useful...
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WATCH OUT FOR THE SHOOTING STARS!
A Guide To The Leonid Meteor Shower
Produced by COCKERMOUTH ASTRONOMICAL SOCIETY
If you're regularly up and about late at night - perhaps walking your dog,
driving to or from work, or taking a short cut through the park on your way
back from the pub - then the chances are that you've seen a few shooting
stars skip or streak across the sky. Did you make a wish? Well, even though
there's no proof that works it's okay if you did, there's no harm in trying,
but you may be surprised to learn that you were wishing on something about as
unromantic as it's possible to be.
You see, shooting stars aren't really stars at all, they're tiny pieces of
dust and grit - 1mm to 1cm wide bits left over from the formation of our
Solar System five billion years ago - which are scattered randomly through
space, spread far, far apart. When the Earth's gravity pulls one in it burns
up in a streak of light as it plunges through our atmosphere at speeds of
over 50 kilometres per second! No, not very romantic.
And as if that wasn't bad enough, shooting stars aren't as rare as people
think. Tens of millions of meteoroids dash themselves against the atmosphere
every day, though only a small percentage of those become visible as shooting
stars. Still, go outside on any clear, Moonfree night and you'll see one
every ten minutes or so... you could easily get through a dozen wishes every
night!
Anyway, as Jennifer Anniston says, "Here comes the science part...
concentrate." Because those one-off shooting stars are unpredictable - they
can appear at any time, and can come from any direction - they're known as
"sporadics". But on certain nights of the year we can see increased numbers
of meteors, and they all appear to come from one part of the sky, from one
particular pattern of stars, or constellation. This phenomena is known as a
"meteor shower", and it happens when Earth ploughs through a stream of dust.
Where does all this dust come from? Okay. Cast your mind back to last Spring.
Remember gazing up at Comet Hale-Bopp and marvelling at its lovely, curved
yellow tail? Well, that was made of billions of tiny particles of dust,
larger bits of grit and furballs of softer, fluffier powder, released from
the comet's icy head as it was melted by the Sun's warmth. Over the next
hundreds and thousands of years all that dust will spread out into a kind of
stream, tracing out the comet's orbit around the Sun.
This isn't unique, it happens to every comet as it goes around the Sun. So,
it isn't hard to add two and two and get four, and to realise that whenever
Earth travels through one of these dust streams more debris will hit the
atmosphere and we will see a shower of shooting stars...
In mid-November - as it does every year - Earth will take a plunge through
one of these rivers of crumbling comet dust, the debris from an Old Faithful
comet called Tempel-Tuttle, and we'll see a meteor shower. Because they'll
all appear to shoot away from the constellation of Leo, the meteors are known
as "Leonids".
The shower is one of the year's most reliable, and every year it treats us to
a good show, allowing people patient and hardy enough to stay up until after
midnight to make a wish every couple of minutes or so.
But... and it's a Big But... this year might be different. Very different.
This year the shower may become a Storm, and for a while you might - might! -
be able to make dozens of wishes every second...!
Why should this year be so different? Well, the dust left behind by Tempel-
Tuttle isn't evenly distributed. The stream is thicker in some parts than in
others. Every 33 years the Earth passes through one of the densest dust
patches within the main dust stream... and in just a few weeks time we will
do so again, and as a result may see a spectacular show in the sky late at
night on the 17th, or before dawn on the 18th.
Just how much dust we'll plough through - and how many meteors we'll see - is
anyone's guess; just to make things extra confusing there are clumps and
ribbons of dust scattered through the stream, giving it a bewildering,
chaotic, 3D structure virtually impossible to model or simulate - but there is
some pretty serious guessing going on, because we may get more than just a
pretty light show.
Each incoming piece of cometary dust is a miniature bullet, travelling at
over 40 miles per second (fast enough to go around the world in 11 minutes!)
so the world's space boffins are understandably nervous about possible damage
to their expensive orbiting toys! There are now more than 500 working
satellites currently orbiting Earth, most of them surprisingly fragile boxes
of sensitive electronics powered by flimsy, sail-like solar panels. Many of
those satellites, including the Hubble Space Telescope, will be carefully
rotated to protect their sensitive instruments as much as possible. You can
bet the cosmonaut crew up on the MIR space station will have their fingers
crossed too! Although space scientists are sure the crew will be in no danger
from the Leonids, during the height of the shower they'll be sheltering in the
Soyuz spacecraft docked to the station.
Meanwhile, back down here on the ground, stargazers the world over are
awaiting the Leonids with breathless excitement, well aware that after years
of waiting and reading about the Great Storms of the past, there is a chance
that the sky will soon blaze with thousands of meteors and fireballs in an
enormous celestial fireworks display!
Unfortunately, the chance of such a spectacle being visible from the US or UK
are slim. Both the US and UK will still be basking in sunshine at the time the
Earth is predicted to encounter the most dust, which is why many meteor
observers are planning to travel eastwards to Japan and East Asia, the
countries which will be, according to predictions, in the front row. However,
we know so little about the actual structure of the Leonid dust stream that
the peak may well occur earlier or later than predicted, in which case
anyone under a clear dark sky might see it. So, wherever you are, keep your
fingers crossed!
We do know from past experience that wherever it's visible from, IF it occurs,
any intense meteor storm will be short-lived, probably just a few hours long
and perhaps less than one hour. It's very important to understand that no-one
is guaranteeing or even predicting a spectacular shower. All we know is that
it will be worth looking for more shooting stars than usual if the sky's
clear.
How to Watch The Show
Watching the Leonid meteor shower will be embarrassingly easy. The only
things you'll need are a clear sky, warm clothing, and your eyes. Oh, and
lots of patience, because there's still a very real possibility that nothing
spectacular will happen, and there'll be just an average display with minutes
between shooting stars.
You should find somewhere dark to observe from, somewhere free of
streetlights and security lights. The darker your observing location, the
more shooting stars you'll see, it really is that simple. Take with you hot
drinks or soup in a flask to keep you warm, and dress for the Arctic, gloves,
hat, the works. Take some snack food too.
Also, take some binoculars with you, because some bright meteors leave
behind glowing trails in the sky, and it's fun to watch them twist and
contort into strange shapes as they're buffetted by winds in the upper
atmosphere.
If you have one, take a deck chair or a sun-lounger so you can sit down or lie
back while observing; standing with your head tilted back for hours is
guaranteed to give you a killer pain in the neck. Oh, and if you can persuade
someone to go with you all the better. Not just because it's safer, but
because talking with someone will keep you awake and make the time go quicker
- and meteor watching is much more fun with a friend too!
As for time... if The Experts are right the peak activity will occur mid-
afternoon our time, when the sky is still bright and the radiant (that's the
area of sky the shooting stars will come from, remember) is still way below
the horizon. It won't rise until around 10.30pm on the evening of Tuesday
November 17th, and, statistically, most meteors will be seen after midnight,
so you should plan on having a late, late night.
Having said that, it's worth watching the sky from around 9.00pm, because we
may see some exceptionally bright fireballs streak across the sky... fingers
crossed again.
So, where do you look? Well, the radiant lies in Leo, a Sphinx-shaped
constellation which lies below and to the right of the Plough. If you face
Leo the meteors will appear to your left and right, above you, behind you, in
all directions, so there's no "right" place to look. Just go outside, face the
north east... and wait. And keep those fingers crossed!
If you want to do more than just watch the meteor shower, you could try taking
photographs of it! All you need is a basic SLR camera with a B setting that
takes you take long exposures using a cable release. Load it with a fast film,
200 or 400 ASA, point it at an area of sky to one side of the radiant - say,
The Plough - and open up the lens to its widest aperture (f2 is good). Begin
your exposure... and cross your fingers that a meteor crosses the camera's
field of view! Keep exposures down to ten minutes or so. When you get the pics
back you'll see the stars have recorded as trails because of the rotation of
the Earth... and you will hopefully have caught a few shooting stars too!
Whatever you do, make sure you at least make the effort to LOOK! Do whatever
you have to do, stay awake with gallons of coffee, or set your alarm really
loud, but get out there and look up, because while there's absolutely no
guarantee we'll see anything extraordinary, but if you're fast asleep you're
absolutely guarenteed to see nothing. And if you miss the Leonids this time
around you'll have a long, loooooong wait for the next show-stopper. You can't
just add 33 years and circle that date in your diary because in 2029 Jupiter's
strong gravity will tug at the dust stream and pull it away from Earth, and
there won't be the potential for another Leonid Storm until 2098 or perhaps
2131!
The bottom line: stay up late on the evening of November 17th and you WILL
see more shooting stars than usual. There's a chance that you'll see LOTS
more than usual, perhaps thousands and thousands.
Finally, if the sky's clear on the previous evening look then too - the storm
might actually occur earlier than The Experts predict...!
Good luck!
Stuart Atkinson
STUARTATK@aol.com
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