The Leonids meteor shower 2009

Hot on the heels of the Taurid meteor shower which peaks a week or two earlier, we have the peak of the Leonids this November.

The Leonids is probably the best known annual meteor shower, and is caused when Earth passes through the dusty debris trails left behind comet 55P\Tempel-Tuttle as it orbits our sun.

As these mostly dust-sized particles (or meteoroids as they are known when they are still out in space) encounter our atmosphere, due to their high relative velocity of 71km/s, these meteoroids cause the air to glow as they slam into air-molecules, breaking them apart and ionizing them. The luminous phenomena produced in this process is what we call a meteor.

Comet 55P\Tempel-Tuttle has a period of 33 years, which means that it makes one complete orbit around our sun once every 33 years. Every time it completes an orbit, a trail of debris is laid down, and over the thousands of years that the comet has been doing this, many hundreds of trails have been formed.

Here is a short animation of just such a trail being created. In this case, the model used shows the creation of the trail laid down during the year 1767, and it's evolution up to the present day. The red rings represent the orbits of Earth and Jupiter. As you can see, over the course of time the debris trail becomes spread out and distorted, mainly due to the gravity of Jupiter.

So when Earth's orbit takes us through parts of space where trails have been left, it can encounter a variety of trails - some older and less dense, and some more recent, where meteoroids have not had a chance to disperse. If we have a close encounter one of these fresh trails, this can give us a meteor storm, such as the great Leonid storms of 1833 and 1966.


This year
Whilst this year is not expected to produce a storm, most researchers agree that quite a strong outburst is likely to occur. There may even be as many as 500 meteors visible (a "half storm"!) every hour at the height of the encounter, if viewed under ideal conditions, although it is not certain, and likely to be nearer to 150-300 per hour.

There are a number of trail encounters that have been predicted, but the most interesting, according to predictions made by J. Vaubaillon are listed below:

1466 Trail
17/11/2009 @ 21:43 UT (may be 0.5-1hr later) = 115/hr

1533 Trail
17/11/2009 @ 21:50 UT = 80/hr

1102 Trail
18/11/2009 @ 3:29 UT = 10-50(?)/hr


The 1466 and 1533, since they occur at more or less the same time, will combine together to create a single peak.

J. Vaubaillon also mentions an earlier encounter on Nov. 17 that may also be of interest to observers:

1567 Trail
17/11/2009 @ 7:27 UT = 25/hr

NASA have compiled complete details of all predictions from various researchers in the form of a PDF document which is available here.

Please note that since this document was published, Vaubaillon has refined his predictions, and lowered the predicted peak rate.


Where?
The expected peak due to the 1533 and 1466 trails will be best observed from China, India, Japan, and Indonesia. Eastern Europe, The middle East, and East Africa will also see the peak, although rates will not be as high there.

Western Europe, and Western Africa will also be able to observe the peak, although it will arrive before midnight local time in these parts, which is when the Leonid radiant is still rising, meaning even lower rates would be expected from here.

However, this is perfect timing for those wishing to see "earth grazers", which only occur when the Leonid radiant is close to the horizon. These are spectacular meteors that skim the upper atmosphere, which means they can often last longer than ordinary meteors, so they can be particularly impressive!

To see these, you will have to venture out at around 9PM local time for mid-northern latitude observes. They are usually few and far between, but it's worth it only if you see one or two.

Although the peaks listed above will probably be the best time to see Leonid meteors, there is always a chance that someone has missed something, so observing on the nights either side of the peak is also recommended for the die-hard observers out there. The Leonids is a shower that usually has quite a narrow (rather than broad) peak, so rather than a gradual increase in rates over successive nights like the Perseid meteor shower in August, there is quite a pronounced increase in rates around the time of maximum. Still, Leonids can be seen as early as two weeks before the peak, and 1-2 weeks after.


Observing
The best way to observe any meteor shower, is lying flat on you back, and looking straight up. It's cold this time of year for may of us, so put on a few layers of cloths and climb into a sleeping bag if you have one.

I like to use a sun lounger, which is comfortable (no having to crane neck) , keeps me off the cold ground, and raises me up a bit so that I have a slightly wider view of the sky. You want the widest, least obstructed view you can get, and you should try to keep any stray light out of your eyes as much as possible. Ideally you want to as far away from civilization as possible, but even if you can not get away, you can still see the brighter meteors, although rates will be reduced due to light pollution. See the links below for more observing tips.

Good luck, and enjoy the show!


Related Links

2009 predictions
J. Vaubaillon
Mikhail Maslov

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

Last years Leonid meteor shower:
Leonid meteor shower 2008 - This week!

Basic visual meteor shower observation techniques:
How to Observe Meteor Showers
How to View Meteor Showers - How to "See More Meteors"




This great video covers almost everything, but I would argue on a few points that were mentioned:

1. It's usually better to be totally flat when observing meteors since you can catch meteors close to any horizon with your peripheral vision when facing directly upwards.

2. If you live in a warm/tropical climate, you might get away with a blanket (or even less) to keep you warm, but I'd advise putting on multiple layers of warm cloths, and jumping into a sleeping bag if you want to observe for any length of time if you live away from the equator. If you are too warm (unlikely in most cases) then you can always remove a layer of cloths or two.

3. The camera exposure times he mentioned could be at the upper end of the scale if you have any light pollution at you're site and/or depending on your equipment/settings/how you want your photo to appear. It's worth experimenting before hand, but if you are using fast lenses/high ISOs (which you should be if you want to catch any meteors, although you may get lucky and catch a bright meteor anyway), exposures can be as short as 5 or 10 seconds. See links below for more info.


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

Photographing meteors:
www.abovetopsecret.com...
www.abovetopsecret.com...

General information:
www.space.com...

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

[edit on 30-10-2009 by C.H.U.D.]

David Asher has just posted predictions for this year's Leonids that agree with the other predictions posted above.

Although the 2009 shower will not produce the storm level activity of the Leonids some years ago, observers in the right part of the world should see some nice outburst level activity. This will be due to material released by the Leonid parent comet, 55P/Tempel-Tuttle, at various past returns, especially those in 1466 (16 revolutions ago) and 1533 (14 revolutions ago).

Source: Armagh Observatory

Just to sum up, we are not sure exactly how many Leonid meteors to expect this year, but where ever you are, try and observe on the 17th/18th. It's likely that you may catch some very bright meteors, especially if you stay out and observe for long enough. Be sure and wrap up warm though

There may be lots, or there may be only a few, but there is only one way to find out!

Good luck to all, and clear skies!

Edit to add - observations as they come in are used to generate a "real time" graph that can be found here.

Results/graphs from previous years can also be found here.

[edit on 10-11-2009 by C.H.U.D.]

Just a day or two to go till peak now!

space.com has a very good article from Joe Rao on this year's Leonids, including detailed info for varied locations on when would be the best time to watch. Well worth a read!

Updating with some Leonid meteor footage recorded over Central Italy, on 16-17-18.11:

Video 1 (download)

Video 2 (link to embedded video)