Meteor Showers (and more)DELETE

Have you ever gone out at night and looked up at the stars? From time to time, you might see a streak of light stretch across the sky. Many people call these “shooting stars”. But they are not stars at all. They are meteors – small chunks of dust burning up in the Earth’s atmosphere.

Meteors, meteoroids, and meteorites are three terms associated with “shooting stars” that many people, including me, mix up.

• Meteoroids are dust and small chunks of rock hurtling through space.
• Meteors are meteoroids that enter the Earth’s atmosphere and streak across the sky with a glowing tail.
• Meteorites are meteoroids that hit the ground.

According to NASA close to fifty tons of “meteoritic material” falls to Earth daily and most of the meteorites found on the Earth come from asteroids. Most meteors are as small as a gain of sand, become visible at around 50 to 75 miles up, and burn up in the Earth’s atmosphere. The light given off by a meteor is caused by compression, which heats the air in the meteor’s path. The air then cools and emits the light we see. Meteors lose mass as they “burn up” in the atmosphere through something called ablation.

Although most meteorites are extremely small, there are a few notable exceptions.

• A large asteroid created the Chicxulub crater near the Yucatan Peninsula 66 million years ago and is thought to have wiped out the dinosaurs.
• The 150-foot-wide Canyon Diablo meteorite impacted what is now Arizona 50,000 years ago and created the Barringer Crater (below).

Bolides are meteors that explode in a fireball. There are two famous “super bolides”.

• A fifty- to sixty-foot-wide meteoroid exploded in the atmosphere above Chelyabinsk, Russia in February 2013.
• A few hundred-foot-wide meteoroid leveled several tens of million trees near Tunguska, Siberia in 1908.

Many meteoroids come from Asteroids, which are larger, mostly irregularly shaped objects, left over from the formation of the Solar System. Asteroids range in size from a few miles in diameter all the way up to the Dwarf Planet Ceres. A few million can be found in the main asteroid belt between the orbits of Mars and Jupiter. Asteroids (and meteoroids) are typically classified as type M (metallic), type C (stony), or type S (metallic-stony) based on their composition.

Comets might look like meteoroids or asteroids, but they are “dirty snowballs” of ice mixed with gas and dust that come from the Kuiper Belt or Oort cloud. As a comet passes close to the Sun, its heat melts the comet and the solar wind pushes material away creating a long tail that stretches for millions of miles.

Meteor Showers are annual events when many meteors can be seen during a single evening or over a period of days. Most meteor showers occur as the Earth passes through the debris field left by a comet (or an asteroid). Meteor showers are named after the constellation from which the meteors appear to radiate and not after the comet. They are best viewed from a dark location on a moonless night. Most peak after midnight and before dawn when the Earth’s night side is facing in the direction of the Earth’s orbit and the direction from which the meteoroids are coming.

Meteor Shower	Associated Asteroid or Comet	Peak Dates (evening to morning)	Approximate number of meteors per hour (per NASA)	NASA Webpage	timeanddate Webpage
Quadrantids	2003 EH1	January 3-4	120	Quadrantids	Quadrantids
Lyrids	Thatcher	April 21-22	18	Lyrids	Lyrids
Eta Aquarids	Halley	May 5-6	60	Eta Aquarids	Eta Aquarids
Perseids	Swift-Tuttle	August 12-13	Up to 100	Perseids	Perseids
Draconids	21P/Giacobini-Zinner	October 7-8	Up to 10	Draconids	Draconids
Orionids	Halley	October 21-22	23	Orionids	Orionids
Leonids	Tempel-Tuttle	November 17-18	15	Leonids	Leonids
Geminids	3200 Phaethon	December 13-14	120	Geminids	Geminids
Ursids	8P/Tuttle	December 22-23	10	Ursids	Ursids

Oh, and just in case you are wondering, Meteorology is the study of the weather and has nothing to do with meteors. The study of meteors, meteorites, and meteoroids is called Meteoritics.