Everything you need to know about the possibility of a strong Leonid outburst in 2009.
The image at the top of this post shows Leonid meteors striking Earth’s atmosphere and creating “shooting stars” in our sky. The shower is happening now, day and night, as our world moves through space, crossing the orbital path of Comet Tempel-Tuttle, the parent comet of the Leonid meteor shower.
The Leonids are usually a modest shower, with typical rates of about 10 to 15 meteors per hour at the peak. But astronomers from Caltech and NASA last year predicted jointly that we may pass through a particularly dense clump of comet debris in 2009. That could mean a brief but strong outburst of meteors. One astronomer in particular, Jeremie Vaubaillon, predicts a theoretical maximum of 500 Leonid meteors for about an hour at the shower’s peak. Asia is favored, but North America might also see more meteors than usual. The reality is … no one can predict precisely.
The astronomers based their prediction on an outburst that took place during the 2008 Leonid meteor shower. In other words, as Comet Tempel-Tuttle orbits the sun, it leaves behind not just one stream of particles, but several streams. Last year, Earth passed through a meteor stream laid down by Tempel-Tuttle in the year 1466. Observers in Asia and Europe in 2008 counted as many as 100 meteors per hour, which led the astronomers to conclude that the 1466 stream is rich in meteor-producing debris.
This year, our planet will pass through the 1466 stream again, but this time we’ll pass more closely to the center of the stream. That central region of the meteor stream should be dense in bits of icy debris left behind by Tempel-Tuttle. Hence the prediction of a rich Leonid meteor outburst – for some – in 2009.
Just remember, these are predictions – not certainties.
Still, predictions are a meteor-watcher’s stock in trade. Plus the moon will be out of the way for this year’s Leonid meteor shower. New moon falls on Monday, November 16. Its absence from the night sky – plus the tantalizing possibility of 500 meteors per hour – will make 2009 an exceptionally favorable year for watching the Leonids.
(Leonid image at right: Ian Griffin)
When should I watch?
Knowing what time to watch is the tricky part this year. Typically, the best time to watch this meteor shower is between the hours of midnight and dawn.
But this year astronomers have predicted the peak of the shower – when we encounter the richest part of the 1466 meteor stream – for November 17, sometime around 22:00 to 23:00 Universal Time. That translates to late afternoon on November 17 (Tuesday) for us in the central U.S. We suggest watching in the hours between midnight and dawn on November 17. That’s your surest bet for seeing some meteors.
But what about the meteor ‘outburst’ of up to 500 meteors per hour? Will we see this outburst – if it materializes – in the Americas? Almost certainly not, if the outburst occurs at the predicted time. However, the Leonids are a notoriously capricious shower, and are certainly capable of defying the most carefully-crafted forecasts. The only way to know for sure if the Lion will whimper or roar – or somewhere in between – is to watch the shower from late night till dawn on November 16-17 and November 17-18. You’d hate to be indoors if there were something to see. Right? And with the new moon falling on November 16, we’re guaranteed of moon-free nights for watching this year’s shower.
So here’s our suggestion for the Leonid meteor shower of 2009, assuming you are in the Americas. First, as we said, try watching between midnight and dawn on November 17. Then – if you want to – step outside on the evening of November 17, in case meteors from the tail end of the outburst (if there is an outburst) are visible.
Where should I watch?
Although we hear lots of reports from people who see meteor showers from yards, decks, streets and especially highways in and around cities, the best place to watch a meteor shower is always in the country. Just go far enough from town that glittering stars, the same stars drowned by city lights, begin to pop into view.
City, state and national parks are often great places to watch meteor showers. Try googling the name of your state or city with ‘city park’ or ‘state park.’ Just be sure to go early in the day and find a wide open area with a good view of the sky in all directions.
Which direction should I look to see the Leonids?
Meteors in annual showers are named for the point in our sky from which they appear to radiate. This shower is named for the constellation Leo the Lion, because these meteors radiate outward from the vicinity of stars representing the Lion’s mane.
If you trace the paths of Leonid meteors backward on the sky’s dome, they do seem to stream from the constellation Leo. The point in the sky from which they appear to radiate is called the ‘radiant point.’ This radiant point is an optical illusion, though, no more real than standing on railroad tracks and peering off into the distance to see the tracks converge. The illusion of the radiant point is caused by the fact that the meteors – much like the railroad tracks – are moving on parallel paths.
In recent years, people have gotten the mistaken idea that you must know the whereabouts of a meteor shower’s radiant point in order to watch the meteor shower. You don’t need to. The meteors often don't become visible until they are 30 degrees or so from their radiant point. They are streaking out from the radiant in all directions. Thus the Leonid meteors – like meteors in all annual showers – will appear in all parts of the sky.
That's why – when watching a meteor shower – it's best simply to find a wide-open viewing area, lie back comfortably and watch as best you can in all parts of the sky. Sometimes friends like to watch together, facing different directions. When somebody sees one, they can call out.
Is this 2009 shower considered a meteor storm?
No. Not this year. Most astronomers say you need more than 1,000 meteors an hour to consider a shower as a storm. And no one is predicting that many meteors this year.
The Leonid shower is known for producing meteor storms, though. The parent comet – Tempel-Tuttle – completes a single orbit around the sun about once every 33 years. It releases fresh material every time it enters the inner solar system and approaches the sun. Since the 19th century, skywatchers have watched for Leonid meteor storms about every 33 years, beginning with the meteor storm of 1833, said to produce more than 100,000 meteors an hour. The next great Leonid storms were seen about 33 years later, in 1866 and 1867. A meteor storm was predicted for 1899, but did not materialize. It wasn’t until 1966 that the next spectacular Leonid storm was seen, this time over the Americas.
For me ?even one meteor can be a thrill. But we have become a world of thrill-seekers. If you want to watch this year’s possibly very rich Leonid meteor shower, just be sure to give it a chance. Find a dark sky location. Bring along a blanket or lawn chair and spend at least an hour watching. And enjoy!