If you missed out on last month's Leonid Meteor Shower, don’t fret. What potentially will be the best meteor display of the year is just around the corner, scheduled to reach its peak during the overnight hours of December 13-14: The Geminid Meteor Shower.

If the Geminids occurred during a warmer month, they would be as familiar to most people as the famous August Perseids. Indeed, a night all snuggled-up in a sleeping bag under the stars is an attractive proposition in summer, and many campers on vacation often independently “discover” the Perseids. On the other hand, it’s hard to imagine anything more bone chilling than lying on the ground in mid-December for several hours around midnight, looking up at a clear sky that has brought radiational cooling and plummeting temperatures since sunset.

But if you are willing to bundle up, this coming Sunday night into early Monday morning will be when the Geminids are predicted to be at their peak. And depending how dark your location is, and how much of the sky you can see, meteors may streak into view that night at an average rate of one or two per minute. The Geminids are—for those willing to brave the chill of a December night—a very fine winter shower, and usually the most satisfying of all the annual showers, even surpassing the Perseids.

Studies of past displays show that this shower has a reputation for being rich both in slow, bright, graceful meteors and fireballs as well as faint meteors, with relatively fewer objects of medium brightness. Many appear yellowish in hue. Some even appear to form jagged or divided paths.

These meteors appear to emanate from a point near the bright star Castor, in the constellation of Gemini, hence the name “Geminid.” The track of each one does not necessarily begin near Castor or even in the constellation Gemini, but it always turns out that the path of a Geminid extended backward passes through a tiny region of sky about 0.2 degrees in diameter (an effect of perspective). In apparent size, that’s less than half the width of the Moon. As such, this is a rather sharply defined radiant as most meteor showers go; suggesting the stream is “young”—perhaps only several thousand years old.

Excellent Viewing Conditions

Unlike the case this year with the August Perseids, this year’s December Geminids will not be hindered at all by moonlight. On Monday morning, the Moon—a narrow sliver of a crescent, just two days before New—will come up over the east-southeast horizon soon after 5:30 a.m. for most locations and will pose very little, if any interference for meteor watchers.

Best of all, Earth is predicted to be passing through the densest part of the Geminid swarm at around 5:00 GMT on December 14. That means that much of Europe and North America will be in excellent position to catch the absolute peak of this display, which should persist for more than several hours. Keep in mind that regardless of where you live, the very best time to watch for the Geminids will come at 2 a.m. local time on Monday morning. At that hour, the constellation Gemini will appear almost directly overhead.

Late Sunday night on through early Monday morning, a single observer blessed with a dark and unobstructed view of the sky might average as many as 60 to 120 meteors per hour —one to two meteor sightings per minute.

Watch for Earthgrazers

Generally speaking, depending on your location, the star Castor begins to come up above the east-northeast horizon right around the time evening twilight is coming to an end. As Gemini is beginning to climb the eastern sky just after darkness falls, there is a fair chance of perhaps catching sight of some “Earth-grazing” meteors early on Sunday evening.

Earthgrazers are long, bright shooting stars that streak overhead from a point near to, or even just below, the horizon. Such meteors are so distinctive because they follow very long paths nearly parallel to our atmosphere. As Gemini climbs higher into the sky, however, these very long paths will become much shorter.

The Geminids will appear noticeably more numerous in the hours after 10 p.m. local time, because the shower’s radiant is already fairly high in the eastern sky by then. As was already noted, the best views come at around 2 a.m., when their radiant point will be passing very nearly overhead. The higher a shower’s radiant, the more meteors it produces all over the sky.

Slowpokes

Because Geminid meteoroids are several times denser than the cometary dust flakes that supply most meteor showers and because of their relatively slow speed with which they encounter Earth—22 mi (35 km) per second—Geminid Meteors appear to linger a bit longer in view than most. As compared to an Orionid or Leonid meteor that can whiz across your line of sight in less than a second, a Geminid meteor moves only about half as fast.

Slow rise . . . rapid decline

The Earth moves quickly through this meteor stream producing a somewhat broad, lopsided activity profile. Hourly rates begin to slowly increase on December 10, when hourly rates will be about one-quarter maximum rates.

After Sunday night, their intensity should drop off more sharply: rates on Monday night/Tuesday morning will have diminished to about 30 to 60 per hour. Yet, there is good reason to keep watching for Geminids even after their peak has passed, for those “late” Geminids, tend to be especially bright. And renegade late stragglers might be seen for a week or more after the night of maximum activity.

Stay warm and "Shower" with a Friend

I brought this up this point earlier, but certainly it should be addressed again: Make sure you're warm and comfortable. Likely your local weather will be more appropriate for taking in a hot bath as opposed to a meteor shower! Meteor watching in December can be a long, cold business. You wait and you wait for meteors to appear. If they don't appear right away, and if you're cold and uncomfortable, you're not going to be looking for meteors for very long!

The late Henry Neely, who for many years served as a popular lecturer at New York’s Hayden Planetarium, once had this to say about watching for the Geminids: “Take the advice of a man whose teeth have chattered on many a winter’s night—wrap up much more warmly than you think is necessary!” Hot cocoa, tea or coffee can take the edge off the chill, as well as provide a slight stimulus.

It's even better if you can observe with a friend. That way, you can keep each other awake, as well as cover more sky. Give your eyes time to dark-adapt before starting.

Asteroid or Dead Comet?

A final point to note are that Geminids stand apart from the other meteor showers in that they seem to have been spawned not by a comet, but by 3200 Phaeton, an Earth-crossing asteroid. Then again, the Geminids may be comet debris after all, for some astronomers consider Phaeton to really be the dead nucleus of a burned-out comet that somehow got trapped into an unusually tight orbit.

Circle November 17 on your calendar, for early that morning a good showing of Leonid meteors appears likely.

According to theoretical predictions by several noted astronomers who specialize in forecasting meteor showers, there might be anywhere from 20 to 30 meteors per hour seen under ideal conditions during the early morning of Tuesday, November 17th.

Actually, Leonid meteors can be seen every year around November 17th. Leonid particles typically are scattered sparsely, so that, in most years, we see only a few Leonid meteors per hour. For North America, this year's enhanced activity results mainly from the Earth passing through a trail of dust emitted by a small comet more than four centuries ago.

Best Views in the East

Observers in the eastern United States will be particularly favored for maximum activity is expected sometime between 3:30 and 5:30 a.m. Eastern standard time, when the radiant of the Leonid shower will be well up in the dark southeastern sky. (A meteor shower's radiant is the perspective point from which all the meteors would appear to originate if their paths were traced backward far enough. The higher the radiant is, the more meteors flash into view all over the sky.) The Leonid radiant is within the so-called Sickle of Leo; a backwards question-mark pattern of stars that outlines the head and mane of the constellation Leo, the Lion. Hence the meteors are known as Leonids. Nevertheless, observers all across North America may experience a good Leonid show with meteors flashing out every few minutes.

Also a big plus in 2009 is the lack of any interference from the Moon. New Moon is on November 16th, so skies will be dark for catching the fainter meteor streaks. And the first light of dawn will not break until shortly after 5 a.m. local time.

Cosmic Garbage to Light Up the Night

The Leonids are caused by cosmic garbage. That may not sound sexy, but it still should make for a good sky show. The meteors are produced by particles that are shed from the Comet Tempel-Tuttle every time it passes close to the Sun during its approximately 33-year orbital journey. Trailing behind the comet is a dirty trail of very small dust particles, generally less than 1 millimeter in size and orbiting the Sun. As the particles run into the Earth's atmosphere they vaporize within a few seconds at altitudes of about 60 miles above our heads.

Astronomers are forecasting that between roughly midnight and 5:30 a.m. on November 17th, the Earth make a 400,000-mile journey through a cloud of particles that was ejected from the nucleus of Comet Tempel-Tuttle back in the year 1567.

Larger particles, up to pebble-size, can produce brilliant meteors known as fireballs, rivaling in luminosity the brightest stars and planets and on rare occasions, even the Moon. Leonids travel at very high speeds through our atmosphere—up to 162,000 miles per hour—and some can leave bright trails of ionized atoms producing trains that can last for many seconds, or even minutes.

Observing Tips

In order to see meteors, the sky must be clear and your selected observing site should preferentially be free of light pollution; the less light, the more meteors will be seen! Notice that Leonid meteors occur in the after-midnight hours. Hence, there is no point in starting your observation much earlier. Diehards who do not want to miss anything of the show should then continue to watch until dawn. Those who cannot afford to stay up that long should focus on a period of, say, one or two hours. The very best interval to watch is expected to be between 3:30 and 5:30 a.m. EST on the morning of Tuesday, November 17th.

Be very aware that it can be very cold in mid-November: you should, of course, wrap-up well in several layers of warm clothing to ward off the cold. For comfortable observing, use a reclining chair and place yourself either in a suitable sleeping bag or under several blankets. While observing, do not fix a particular star, but scan the area of sky from the north-west to east. Look relaxedly and patiently across a wide area of sky and wait for a shooting star to appear.

Leonid Storms

Old chronicles contain references to past Leonid meteor storms back to the 10th century A.D. The best-known Leonid meteor storms are those of 1833 and 1966, when literally tens of thousands of meteors darted across the skies during the peak hour! The 1833 meteor storm was so spectacular that it in fact launched meteor research as a branch of astronomy.

Unfortunately, we cannot expect a repeat of that in 2009, but with Leonids appearing at an average of every two or three minutes, a very entertaining meteor display is anticipated.

Good Luck and Clear Skies! And, feel free to share your experiences in the comments section of this post.