The Leonid Meteor Shower Peaks Wednesday: Tips for Skywatching

This is the week that the famous Leonid meteor shower will be reaching its peak, and the best viewing of these ultra-swift "shooting stars" should come before dawn on Wednesday and Thursday (Nov. 17 and 18).?

There is always some uncertainty in the number of meteors the Leonid shower will produce, but the best consensus from most meteor experts indicates that this year viewers should expect to see approximately15 to 20 meteors per hour if they have clear skies.

Prime-time Leonid viewing this year will be around two to three hours before your local sunrise. [Gallery: Spectacular Leonid Meteor Shower Photos]

A waxing gibbous moon will set about 1 1/2 to 2 1/2 hours before dawn, and therefore should not hinder the viewing for prospective meteor watchers during that time frame. Leonid meteors appear to fan out from the constellation Leo, the Lion.

This sky map shows where to look to see the Leonid meteor shower this week.

How to watch the Leonids

If you have a lawn chair that reclines, use it during your search for Leonid meteors since it will help keep your neck from getting stiff as well as make it easier to look at the night sky.

And remember that for most parts of the country, November nights can be quite cold ? more apropos for a hot bath as opposed to a meteor shower. So take along some blankets or better yet, a sleeping bag, as well as a thermos of hot tea or coffee with you.?

It?s always more fun if you have someone watching with you (or if you're watching with a group of people) ? so try "showering" with a friend. Let your eyes relax and don't worry about looking in any one specific spot.

Relaxed eyes will pick up on any movement and will help you spot more meteors this way. And you don't need binoculars or a telescope for watching a meteor shower. In fact, using one makes it far less likely for you to see any meteors at all because it considerably reduces the amount of sky you can see at any one time.

On the other hand, the Leonids are known for occasionally producing outstandingly bright meteors known as fireballs ? brilliant meteors that explode in a fiery flash called bolides. Either of these kinds of meteors is capable of leaving an incandescent streak or trail behind it that can linger for many seconds, or even minutes. If you have binoculars, you can use them to get a close-up view of a luminous trail and watch as high altitude winds bend and distort it as it gradually fades from view. 

Watching a meteor shower consists of lying back, looking up at the sky ? and waiting. If they're indeed active on the mornings of Nov. 17 and 18, the Leonids will produce ? on average ? a meteor sighting about every four or five minutes under a dark country sky.

Any light pollution or obstructions like tall trees or buildings will reduce the count considerably. By these standards, the 2010 Leonids will pale in comparison to the performances in the early part of this decade, yet possibly will be comparable to the October Orionids, which are usually categorized as a "good" display.

A Leonid is one whose path, if traced backward across the sky, intersects a spot inside the curve of stars that marks the "blade" of the Sickle of Leo. The Sickle begins rising out of the east-northeast sky after about 11 p.m. local standard time and is poised high in the south as dawn begins to break.?

The annual Leonids

The Leonid meteors return each year when Earth passes through the comet's rubble river. [Top 10 Leonid Meteor Shower Facts]

At approximately 33-year intervals, when Comet Tempel-Tuttle comes closest to the sun in its orbit, (a point called perihelion), it sheds a significant amount of material. This creates knots of material along its orbit. When Earth passes through one of these knots, viewers might possibly see hundreds or even thousands of meteors per hour at the shower's peak.

Just such a circumstance occurred after Tempel-Tuttle passed perihelion in 1998. Between 1999 and 2002, Earth passed through several knots of material and we were treated to spectacular storms of Leonid meteors.

But if Earth simply passes through the normal section of the comet's debris trail, the number of meteors visible will be much lower. That type of condition is on tap for this week. The Earth will not encounter any dusty knots of comet debris, but instead will pass through a region of particles that are evenly distributed and fairly far apart.?

Meteor astronomer, Jeremie Vaubaillon of the Institut de Mecanique Celeste et de Calcul des Ephemerides in France, has mapped Earth's path through this year's Leonid stream.

Vaubaillon's map shows that Earth will interact with particles from Nov. 8 to 24, but the greatest concentration of particles will be encountered between Nov.17 and 18.

After midnight, the only meteoroids escaping collision are those ahead of the Earth and moving in the same direction with velocities exceeding 18.5 miles per second (30 kilometers per second). All others we will either overtake or meet head-on.

But before midnight, when we are on the back side, the only meteoroids we encounter are those with velocities high enough to overtake the Earth. Therefore, on average, morning meteors appear brighter and faster than those we see in the evening.?

And because the Leonids are moving along in their orbit around the sun in a direction opposite to that of Earth, they slam into our atmosphere nearly head-on, resulting in the fastest meteor velocities possible: 45 miles per second (72 kps).? Such speeds tend to produce bright meteors, which leave those aforementioned long-lasting streaks or trains in their wake.

Also, as Leo is beginning to climb the eastern sky near and before midnight, there is a small chance of perhaps catching sight of an "Earth-grazing" meteor.

Earth-grazers are long, bright shooting stars that streak overhead from near to even just below the horizon. Earth-grazers are distinctive because they follow a path nearly parallel to our atmosphere.

On Nov. 16 and 17 at around 11 p.m. and in the hour or two thereafter ? as the Sickle of Leo rises ? is the time with the most promise of seeing an "Earth-grazer."

Moon cuts in early

A significant drawback to this year's Leonid display will be a bright waxing gibbous moon that late on the evenings of Nov. 16 and 17 will be located against the dim stars of the constellation Pisces, the Fishes.

It will light up the sky on these nights and almost certainly will squelch any of the fainter streaks that might otherwise be seen. But in the after-midnight hours, the moon will be heading down into the western sky, ultimately setting at around 2:45 a.m. local time in the predawn hours of Nov. 17 and 3:45 a.m. on Nov. 18.

From the time of moonset, until around 5:15 a.m. ? when the first streaks of dawn begin to appear in the east ? the sky will be dark and moonless. That interval will provide you with your best opportunity to see any Leonid meteors.?

Good luck and clear skies!

• Top 10 Leonid Meteor Shower Facts
• Images - The Best of Leonid Meteor Shower, 2, 3, 4, 5
• The Leonid Meteor Shower Revealed: Shooting Star Show's Brilliant History

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y.