Catch a Falling Star: Part One
Meteors - commonly known as shooting stars or falling stars - are fragments of stone, nickel, and iron from space, which fall through the sky. It is possible to see a meteor or two on any clear night, and on dark moonless nights you may be able to count six or seven meteors an hour.
On certain special nights, you may see meteors in far greater numbers. Then you may count 60 or more meteors an hour! This is called a meteor shower. August has long had a reputation for an abundance of meteors. Every year around this time, newspapers tell their readers to watch the sky for a meteor shower.
There are billions of meteors scattered around the sun, but they are not evenly spaced. A big shower of shooting stars comes when the earth runs into a stream of meteors. These meteor streams are usually made up of debris from the tails of comets. Other meteors may be wayward rocks from the asteroid belt, dusty remnants from the creation of the solar system, or the results of collisions between space material and the moon or nearby planets.
When meteors come close enough, the earth's gravity pulls them in. As meteors fall through the atmosphere, they travel at a speed of 30-40 miles a second. When you first see one, it's about 60 miles above the earth. By the time it disappears, most are still about 40 miles above the earth. A meteor's friction with the air causes it to glow white-hot. Once in a while, an extra bright meteor, or fireball, appears in the sky. Fireballs are so bright that they can even be seen during the day.
Many meteors are no bigger than a pea, a grain of rice, or a piece of sand. Most of these meteors are incinerated in the atmosphere before they hit the ground. However, some big meteors survive their journey through the atmosphere and hit the earth, falling at the rate of about a dozen per day.
Shooting stars puzzled the people of long ago. An old Egyptian record tells about a night when the stars all jumped around like grasshoppers. The Romans believed that a shower of shooting stars meant that their gods were angry. The earliest recorded observation of the Perseid meteor shower was made by Chinese astronomers in 36 AD.
THE PERSEID METEOR SHOWER
The astronomical highlight of the summer is in early August, the time of the Perseid Meteor Shower. This is the most famous of all meteor showers due to its dependability. It never fails to provide an impressive display, and with its summertime appearance, it's the most common meteor shower viewed by backyard sky-watchers.
The Perseid meteor shower typically lights up the night sky with an average of 60 meteors per hour - that's one meteor per minute! Occasionally it has peaked in a meteor storm with as many as 200 meteors per hour. (How many meteors per minute would that be?) Either way, the Perseid meteor shower is an astronomical event worth staying up late for - as long as clouds don't spoil the view!
The Perseid meteor shower generally lasts from about July 17 to August 24. It usually peaks from August 11-12, with about 80-100 meteors per hour.
When you see one of these meteors, mentally trace it backwards. The point from where the meteors appear to radiate is located within the constellation Perseus. Even though the Perseid meteors radiate from the northeast in the constellation Perseus, they are visible in all areas of the sky. The best way to see the display is to get away from bright city lights. The darker the sky, the more meteors you will see. Focus your gaze halfway up from the horizon, in the direction which is darkest.
In general, prime time to see the display is from midnight to dawn. You can start the watch as early as 9:00 pm, though the meteor rates will be considerably less. Decent numbers of Perseids can be seen beginning around 10:00 p.m., but the later you stay up, the more active the shower will become. The best show picks up after midnight and continues until dawn. (Check the Moon phase, too - the best time to look is during a New Moon, before the Moon comes up, or after the Moon has set. A full Moon or almost full Moon will make it difficult to see any meteors.)
The Perseids have also been called the "Tears of Saint Lawrence", since meteors seemed to be in abundance during the August 10th feast day of that 3rd century Christian martyr. Credit for the discovery of the shower's annual appearance is given to Quételet (Brussels), who, in 1835 reported a shower occurring in August that emanated from the constellation Perseus.
The Perseid meteors originate from the Comet Swift-Tuttle. This comet enters the inner solar system once every 130 years, most recently in 1992. As it passes near the sun, some of its ice evaporates, releasing mineral grains were trapped within it. Comet Swift-Tuttle is said to shed about 55 tons of dust-grain particles every second! As the earth orbits around the sun, it intersects with the elongated orbit of Comet Swift-Tuttle. A small fraction of that debris becomes the Perseid meteors. (See http://meteorshowersonline.com/perseids.html for additional info.)
OTHER METEOR SHOWERS
Orionids - The Orionid meteor shower appears from October 2 until November 7 and peaks around October 21 at about 20 meteors per hour. (See http://meteorshowersonline.com/orionids.html for additional information on the Orionids.)
Leonids - The Leonid meteor shower appears from November 14-21 and peaks around November 17. There is (See also http://meteorshowersonline.com/leonids.html for additional information on the Leonids.)
Geminids - The Geminid meteor shower appears from December 7-17 and peaks around December 14 at 120 meteors per hour. (See http://meteorshowersonline.com/geminids.html for additional information on the Geminids.)
While the above meteor showers are the most popular, there are also several minor meteor showers such as the Lyrids (April), Eta Aquarids (May), Delta-Aquarids (July/August), Ursids (December), and Quadrantids (January).
METEOR OBSERVATION TIPS
The best way to observe a meteor shower is to be patient. Make sure you're comfortable and wear appropriate clothing for the weather. Lie outside in a reclining lawn chair - or for the Perseids, in an inflatable lounge chair in your backyard pool! Look up, scanning the sky with your eyes and making use of your peripheral vision. No binoculars or telescope are needed. To maintain your night vision, avoid looking at any lights. Use a flashlight with a red beam or attach a piece of red cellophane over a regular flashlight. The red color provides enough light to see by, while allowing your eyes to remain fully adapted to the dark.
While the brightest meteors will be visible even from urban areas, try to find the darkest spot you can or else a lot of the fainter meteors will be missed. Meteors go so fast that by the time you say "Look at that one!" it's already gone. Remember, the expected rate of meteors is given as an average, so don't be disappointed if you don't see exactly one meteor per minute. You may see 20 meteors in less than 2 minutes, and then not see another meteor for another 20 minutes!
METEOROID - A rock-like object in space that is similar to but smaller than an asteroid.
Did You Know…?
The following verse by Samuel Taylor Coleridge from The Rime of the Ancient Mariner may have been inspired by the Leonid meteor shower that he witnessed in 1797.
"The upper air burst into life!
Comets and Meteor Showers, by Paul P. Sipiera, 1997. (An informative introduction to the subject for ages 9-12.) A book for children 4 to 8 years old. This one describes what comets are and their relationship to meteor showers.
Comets, Meteors, and Asteroids, by Seymour Simon, 1994. (A picture-book introduction with scientific information.)
Cosmic Phenomena : Comets, Meteor Showers, Eclipses, by Gabriele Vanin, 1999. (This lavishly illustrated introduction to the celestial phenomena visible to the unaided eye is a well-documented reference work, excellent learning tool, and fine coffee-table showpiece. It covers the Great Comets, meteors as well as some of the biggest meteor showers in history, and eclipses of both the sun and the moon.)
Discover Arizona's Night Sky (Arizona Highways), by Raymond Shubinski and Frank Zullo, 1991. (A beginner's guide to stargazing in Arizona, with handy reference charts, seasonal sky references, photos of the constellations, and directions on how to build a simple tracker to use with your camera for time exposures of the stars.)
Meteor! by Patricia Polacco, 1996. (The meteor that crash landed in Grandma and Grandpa's yard set off a chain of gossip and events that brings excitement to the whole town. Based on a true event in the author's life, she carries a piece of the meteor with her when she speaks to schools.)
Meteors and Meteorites: Voyagers from Space, by Patricia Lauber, 1989. (Learn about ancient collisions, dinosaurs and meteorites, asteroids and comets, a space object that hit Siberia in 1908, and raining rocks in Connecticut.)
Meteors: Sky & Telescope Observer's Guides, by Neil Bone, 1994. (This book tells how to observe and keep records of meteor showers, and discusses the history of meteor study.)
Meteors: The Truth Behind Shooting Stars (First Book), by Billy Aronson, 1997. (This book for 9- to 12-year-olds is well-illustrated with drawings and photographs to explain what meteors are and where they come from. Aronson explains the differences between meteors, meteorites, and meteoroids, and there is even a chapter on how to observe a meteor shower.)
The Heavens on Fire: The Great Leonid Meteor Storms, by Mark Littmann, 1999. (This book focuses on the Leonids, and publication coincided with the Leonid meteor shower in mid-November 1999. It also introduces the great founding scientists, the history of meteors, potential dangers to Earth, and advice on how best to observe a meteor shower.)
http://skyandtelescope.com/observing/objects/meteors (An introduction to meteors, meteor observing tips, meteors that changed the world, and upcoming meteor showers.)
http://comets.amsmeteors.org (Comets and Meteor Showers: an internationally recognized site maintained by Gary Kronk, containing excellent historical and reference information on comets and meteor showers, along with a meteor observing calendar and WWW Links.)
http://amsmeteors.org (The American Meteor Society: information about meteors, meteor showers, meteoric fireballs, and related meteoric phenomena.)
www.seds.org/nineplanets/nineplanets/meteorites.html (Meteors, Meteorites, and Impacts: a highly informative site.)
www.telescope.com (Click on "In the Sky Tonight" to read a Sky Summary of what's visible in the sky for the month.)
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