A meteor is a streak of light in the sky caused by a meteoroid crashing through Earth’s atmosphere.
Meteoroids are lumps of rock or iron that orbit the sun. Most meteoroids are small fragments of rock created by asteroid collisions. Comets also create meteoroids as they orbit the sun and shed dust and debris.
When a meteoroid enters the Earth’s upper atmosphere, it heats up due to friction from the air. The heat causes gases around the meteoroid to glow brightly, and a meteor appears. Meteors are often referred to as shooting stars or falling stars because of the bright tail of light they create as they pass through the sky. Most meteors occur in Earth’s mesosphere, about 50-80 kilometers (31-50 miles) above the Earth's surface.
Even the smallest meteors are visible from many kilometers away because of how fast they travel and how brightly they shine. The fastest meteors travel at speeds of 71 kilometers (44 miles) per second.
The faster and larger the meteor, the brighter and longer it may glow. The smallest meteors only glow for about a second while larger and faster meteors can be visible for up to several minutes. Although thousands of meteors fall during the day, meteors are best observed at night, when the streaks of light are visible in the dark sky.
Meteors appear in different colors, depending on the chemical composition of the space rock and the air it is passing through. A meteor with high iron content, for instance, will appear yellow. A meteor with high calcium content may appear as a purple streak of light.
Scientists think up to 50 metric tons of meteors fall on the Earth each day, but most are no bigger than a pebble. Meteors that don’t burn up in the atmosphere strike Earth’s surface. These meteors are called meteorites.
Types of Meteors
Meteors are described by their size, brightness and proximity to Earth.
Earthgrazers are meteors that streak close to the horizon and are known for their long and colorful tails. Some earthgrazers bounce off Earth’s upper atmosphere and re-enter outer space. Other earthgrazers break up in the atmosphere and streak through the sky as falling stars.
The most famous earthgrazer is probably the “1972 Great Daylight Fireball,” which entered the atmosphere over the U.S. state of Utah, streaking through the sky at 15 kilometers per second (9 miles per second). Thousands of people reported seeing the meteor. The earthgrazer exited the atmosphere over the Canadian province of Alberta.
Fireballs are larger meteors, ranging in size from a basketball to a small car. Fireballs have brighter and longer-lasting light than earthgrazers. The International Astronomical Union describes a fireball as a “meteor brighter than any of the planets.”
Fireballs are probably the most common type of meteor. Members of organizations such as the American Meteor Society report hundreds of sightings every year. As of July 2014, for instance, more than 1,500 fireballs were reported in the United States. Some were seen only in a small area, while others were reported by stargazers across several states.
Bolides are even brighter and more massive than fireballs and often explode in the atmosphere. These explosions can be heard and even felt on the Earth’s surface. Some astronomers classify bolides as fireballs that produce a sonic boom as they streak through the atmosphere.
Certain bolides, known as superbolides, are so bright and create such a large explosion that they become natural hazards, and dangerous to people and communities. The superbolide meteor that passed over Chelyabinsk, Russia, in 2013 exploded with the energy of around 500 kilotons of TNT. Its shock wave shattered windows in thousands of apartment buildings and sent more than 1,200 people to the hospital for injuries. The Chelyabinsk meteor was so bright—30 times brighter than the sun at its most intense—that it left people with skin and retinal burns. Scientists are studying the Chelyabinsk event to better understand how vulnerable human life is to space object collisions, and to develop technologies that protect Earth from them.
Meteor Showers
Usually, just a few meteors are visible over the course of an hour, but sometimes the sky is filled with lights that look like heavenly fireworks. These meteor showers occur when the Earth passes through the orbit of a comet.
Comets shed particles that appear as a dusty trail behind the “dirty snowball” of rock, ice, and gas that makes up the comet’s nucleus. As the Earth passes through a comet’s tail, the rocky debris collides with our atmosphere, creating the colorful streaks of a meteor shower. Meteor storms are even more intense than showers, defined as having at least 1,000 meteors per hour.
All the meteors in a meteor shower seem to come from one spot in the sky. This spot is called the radiant point, or simply the radiant.
Meteor showers are named after the constellation in which their radiant appears. The source of the meteors is not the constellation, of course, but rather the comet from which they have broken off. For example, the Leonid meteor shower appears to produce meteors falling from the constellation Leo, but are actually debris from Comet Tempel-Tuttle. Visible every November, the Leonids are considered some of the fastest and longest-lasting meteors. Other important meteor showers include the Perseids, the Orionids, and the Geminids. Like the Leonids, they are predictable events, occuring yearly at specific times.

One of the Perseids burns up in Earth's atmosphere.
Photograph by Steve Gifford, MyShot
Tunguska
The largest meteor air burst in recorded history occurred over the forests of Siberia, Russia, near the Tunguska River in 1902. The so-called Tunguska Event leveled millions of trees and exploded with the power of about 12,000 kilotons of TNT.
Tecumseh
Communities and cultures all over the world have been familiar with meteors for hundreds and even thousands of years. The name of the great Shawnee leader Tecumseh, for instance, means “Shooting Star.”
Bright Nights
The most brilliant meteor shower in recorded history happened on November 12-13, 1833, when tens of thousands of meteors lit up the sky in just four hours. In contrast, most showers produce fewer than 100 meteors an hour. The 1833 display was one of the Leonid showers that occur every November.
asteroid
Noun
irregularly shaped planetary body, ranging from 6 meters (20 feet) to 933 kilometers (580 miles) in diameter, orbiting the sun between Mars and Jupiter.
astronomer
Noun
person who studies space and the universe beyond Earth's atmosphere.
bolide
Noun
unusually large, bright meteor.
classify
Verb
to identify or arrange by specific type or characteristic.
collision
Noun
crash.
comet
Noun
celestial object made up of ice, gas, and dust that orbits the sun and leaves a tail of debris.
Comet Tempel-Tuttle
Noun
comet that orbits the sun every 33 years.
composition
Noun
arrangement of the parts of a work or structure in relation to each other and to the whole.
constellation
Noun
group of stars that form a recognizable shape.
debris
Noun
remains of something broken or destroyed; waste, or garbage.
dust
Noun
microscopic particles of rocks or minerals drifting in space. Also called cosmic dust or space dust.
earthgrazer
Noun
meteor that enters Earth's atmosphere and usually leaves again.
explosion
Noun
violent outburst; rejection, usually of gases or fuel
fireball
Noun
very bright meteor.
fragment
Noun
piece or part.
friction
Noun
force produced by rubbing one thing against another.
gas
Noun
state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.
intense
Adjective
extreme or strong.
Leonid meteor shower
Noun
annual event, usually in November, when debris from the tail of Comet Tempel-Tuttle fall as meteors. Also called the Leonids.
local
Adjective
having to do with the area around a specific place.
Mars
Noun
fourth planet from the sun, between Earth and Jupiter.
massive
Adjective
very large or heavy.
mesosphere
Noun
region in Earth's atmosphere between the stratosphere and the thermosphere, about 50-80 kilometers (31-50 miles) above the Earth's surface.
Noun
rocky debris from space that enters Earth's atmosphere. Also called a shooting star or falling star.
meteor shower
Noun
large amount of rocky debris falling into Earth's atmosphere, usually when Earth passes through the orbit of a comet.
microscope
Noun
instrument used to view very small objects by making them appear larger.
natural hazard
Noun
event in the physical environment that is destructive to human activity.
observe
Verb
to watch.
observer
Noun
someone who watches, or observes.
occur
Verb
to happen or take place.
orbit
Noun
path of one object around a more massive object.
outer space
Noun
space beyond Earth's atmosphere.
particle
Noun
small piece of material.
pebble
Noun
very small, rounded rock.
predictable
Adjective
regular or able to be forecasted.
protect
Verb
to take action to prevent injury or attack.
proximity
Noun
nearness.
radiant point
Noun
spot in the sky from which a meteor shower seems to originate.
retina
Noun
sensitive tissue at the back of the eye that receives images and sends signals to the brain about what is seen.
rock
Noun
natural substance composed of solid mineral matter.
shed
Verb
to release or cast off.
shock wave
Noun
moving, measurable change in pressure and density of a material.
sonic boom
Noun
loud noise caused by sound waves as an object travels at supersonic speed.
specific
Adjective
exact or precise.
tail
Noun
stream of gas or dust debris behind a comet.
visible
Adjective
able to be seen.
vulnerable
Adjective
capable of being hurt.
Articles & Profiles
- National Geographic News: Leonid Meteor Shower Most Intense for Decades
- National Geographic News: Meteor Dust May Affect Weather, Study Says
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