Leonids 2007

It's that time of year again...

Every November our Earth ploughs through the dust trails left by comet 55P\Tempel-Tuttle during it's regular forays every 33 years into our inner-solar system, giving rise to what is known as the Leonid meteor shower. It may only be dust-sized particles (most are no bigger than grains of sand), but these tiny bits of comet pack a punch since they slam into our atmosphere at a mind boggling 71km/sec, causing the air around them to glow brightly, such is the intensity of of their interaction with our atmosphere.

The process is so violent, that the particle is completely consumed in well under a second in many cases, although larger meteoroids (as they are known before any contact with our atmosphere) can last several seconds, and produce a fireball (very bright meteor) which can in some cases rival the moon in luminosity. The Leonids are well known for producing fireball class meteors, and in most years there is a liberal scattering of bright meteors and fireballs amongst the dimmer shower members which usually make up the majority of the population.

This is not always the case however, and the "population index" (a measure of the ratio of bright to dim meteors) as it is known, can vary widely from year to year as we pass through different combinations of dust trails. In recent years, great strides have been made in understanding how these trails form, evolve, and the effects which ensue when these trails are encountered each year. The trails are modelled on computers, taking into account such parameters as ejection-velocity and gravitational perturbations caused by the planets when they come into close proximity of the trails.

The up-shot of all this is that we now have fairly accurate predictions for our year-to-year encounters with the dust trails, but just like climate models, it's almost impossible to take all factors into account, so the predictions should never be assumed to be 100% accurate.

This year is no exception, and I urge all to go out and look for meteors on the nights surrounding this years peak on the night/morning of the 18th/19th. Nothing extraordinary is predicted, but we won't know for sure until after the show has subsided, and without people looking, we might not even know of any unusual activity. It's the observations that people make, that help us to refine the models, which in turn will mean more accurate future predictions. So dust off your sleeping bags and lawn-chairs, find a site as far away from artificial lights as you can get, and enjoy one of nature's greatest night-time spectacles - you never know, you might be whiteness to an historic meteor shower! Don't forget to take a camera too, if you have one.


Related Links :

2007 Leonid Predictions:
feraj.narod.ru...
/2qxmkj

Leonid shower history and observations:
meteorshowersonline.com...

Basic visual meteor shower observation techniques:
rtpnet.org...
www.astronomy.com...

Advanced visual meteor shower observation techniques:
www.imo.net...

Photographing meteors:
www.abovetopsecret.com...

General information:
www.space.com...

Organizations and mailing lists:
www.imo.net...
www.amsmeteors.org...
tech.groups.yahoo.com...

Good luck and clear skies!

[edit on 8-11-2007 by C.H.U.D.]

[edit on 8-11-2007 by C.H.U.D.]

An excellent post. This is a need to copy guide for those wanting to view the sky on the 17/18th. There's nothing like a brisk fall night watching the sky. It puts things in perspective somehow. (And snuggling with your sweetie under a blanket makes it even better. )

Good links, and plenty of them. Thanks C.H.U.D. Applauded and starred and flagged.

Great post!

Isn't it amazing that the dust that we'll be passing through comes from the dust trail left by the comet passing in 1932?

The passing will be a little less eventful than last year's, with a max of only about 30 an hour expected. The peak is expected to be between 10:36 PM and 11:03 PM Universal Time on November 18th.

So, that would translate to about 5:36 and 6:03 PM, Eastern Standard Time, meaning around sunset look towards the Northeast, near the horizon. They might be hard to see if you're horizon is obscured by trees, buildings, etc. Also, if you're near a city, haze could be a problem as well.

Good luck in your observings, C.H.U.D.!

Nice C.H.U.D !!
Alot of info there and I'll be looking at them on November 18th. Thanks for reminding me about Leonid Shower I almost forgot about this. I hope I can get a good look at them.

Thanks guys

NGC2736 - Agreed! I could never tire of watching the stars

cmdrkeenkid - There will also be the occasional meteor from the 8-revolution trail created around the comet's 1733 return, and even earlier trails..



There are even more ancient meteoroids floating around out there too, which could have come from trails laid down thousands or perhaps even 10's of thousands of years ago. Most of these are so dispersed that they make up the background of the shower, with the dust from the more recent trails giving us the more defined peaks and sub-peaks in the shower. The background activity is already present now (perhaps 1 per hour visible from rural skies), and has been with us since the start of the month. After the peak, it'll start to fall off and be gone by the end of the month.

Your post also reminded me - for those of you who are in a time-zone where the the 11PM UT peak occurs close to sunset, go out as soon as it's getting dark, and you might see some Leonid "earthgrazers", which are often long and beautiful! They are quite rare though, so you need a little luck, and clear horizons to the North, East, and South will help. They will always travel away from the Eastern horizon... sometimes low down and parallel with the horizon in the North or the South, but also directly overhead.

The window for earthgrazers only lasts for about 40-80 minutes depending on where you are, since the radiant needs to be within 10 or 15 degrees of the horizon (below or above) for the geometry to be right for 'grazers. After this, meteors start to look stubbier and fore-shortened. They also appear to move faster and don't last as long, which is due to their hight entry angle, compared to 'grazers, which as their name implies only graze the atmosphere at a low angle, thus prolonging their life.

If anyone is interested in working out their own window, it can be done on planetarium software, or , a program called MetShow which shows you where the currently active shower radiants are. It works much like planetarium software, but simplified. The interface takes a little getting used to, but you soon get the hang of it after a little playing around. It's also a stand-alone program (so no install - just extract, and run), which is nice.

That's me done for the mo. I'll be back with more soon, but before I go, here are two more predictions for this years shower, again in line with the others posted so far. 30 - 40 visual meteors per hour at peak would be a safe bet I think.

star.arm.ac.uk...
leonid.arc.nasa.gov...

Long trails!

Is it just me, or is there a serious lack of news coverage for this years Leonids? Even the Perseids made the BBC news here in the UK this August, but there has been virtually nothing on the Leonids, and it's just 3 days away. Usually there is something on Spaceweather.com/NASA and many other sites out there by this time!

All I can find is this from astronomy.com (apart for a few posts on small forums):
www.astronomy.com...

Perhaps Holmes is stealing the show ? Or perhaps someone does not want people to watch this years Leonids ?!! Might be a possibility, or just my over active imagination + spending too long here on ATS!

Whatever the case, I think it's worth reminding everyone to go out and watch the sky this weekend. Hope you get clear skies and good rates!

reply to post by C.H.U.D.


I just wanted to say that I really am impressed by all the links you bring us on these things. It makes it so easy for us computer/net dummies.

Thank you and a job well done.

Thanks for the heads up! I'll keep my eyes on the skies because I agree you just never know what to expect. I just hope it's not too cloudy.

Thanks NGC2736 and CyberTruth - Just doing my bit to keep ATSers informed.

It seems I may have spoken too soon, spaceweather.com now has a short blurb about the Leonids.

Trying to keep optimistic here, but it looks as though much of the UK will be clouded out for the peak. Hopefully it'll pass in time for at least some clear skies!