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.

Sky watchers in the Tri-State Area may get a look at an odd artificial cloud on Saturday night (Sep. 19) after it’s released from the fourth stage of a rocket set for launch from NASA’s Wallops Flight Facility on Virginia’s Atlantic Shore.

The cloud of aluminum particles from the rocket’s exhaust is expected to provide scientists with insights into the physics of “noctilucent clouds,” the highest natural clouds (around 50 miles up) that form in the Earth’s atmosphere.

The experiment, called “Charged Aerosol Release Experiment” (CARE), is being conducted by the Naval Research Laboratory and the Pentagon’s Space Test Program. Also involved are NASA, the University of Michigan, the Air Force Research Laboratory, Clemson, Stanford and Penn State universities, the University of Colorado and MIT.

The launch window for the experiment opens at 7:32 p.m. Saturday, and closes at 7:49 p.m. Weather forecasters gave the launch a 90 percent chance of favorable weather. However, clear skies are also needed up and down the coast to provide multiple camera locations with a view of the cloud.

Sunday, September 20, is the backup date for the launch. After that, the next opportunity would come next month.

The experiment is being carried by a 65-foot Black Brant 12 rocket, a sub-orbital vehicle used frequently by scientists at Wallops. The rocket is programmed to climb 180 miles above the Earth—much higher than the altitude of natural noctilucent clouds—and 98 miles down range (east) from Virginia’s Atlantic Shore.

Observers should watch for the cloud to be released about six minutes after launch. If skies are clear, the sinuous white cloud should become visible low in the southern sky after its release.

You can follow the launch via Webcast, on Twitter, or by phone at 757-824-2050.

And as always, those who see it are invited to come back here and leave comments describing the event for those who miss it.

At 110 stories, the World Trade Center twin towers were tall enough for the Sun to set nearly two minutes later for people on the top floors than for people on the bottom floors.

City of Stars article: Sunset on the World Trade Center

As always, but especially today, keep looking up.

-NDTyson