Meteoroids, meteors, meteorites, comets, and asteroids are all related to “shooting stars.” But, what to call an object depends on its location and composition. Here is a look at the differences between these objects.
Asteroids
Asteroids are minor planets, including some dwarf planets. They are rocky and orbit a star. Examples of asteroids include Ceres (a dwarf planet), Vesta, and Pallas. Technically, not all minor planets are asteroids. Asteroids are rocky bodies ranging in size from one meter to several hundred meters that are found within the orbit of the furthest true planet of a solar system. Some asteroids are dead comets, which have lost the volatile components that give comets their tails.
Comets
Like asteroids, comets orbit a star. They may contain rocks or dust, but always have a lot of ice. When comets near their star, the volatile ice warms and releases gases, producing a visible atmosphere and tail. Comets usually have highly eccentric elliptical orbits that extend beyond the planets into the Kuiper belt.
Meteoroids
Meteoroids are rocky fragments of asteroids, comets, moons, and planetary collisions. They are much smaller than asteroids, ranging in size from tiny grains up to a meter. Smaller particles are called space dust or micrometeoroids. Like other objects, meteoroids are affected by gravity, but the event that formed them often sends them off on an usual trajectory. In our solar system, most meteoroids come from the asteroid belt, but a few come from comets and fragments of the Moon and Mars formed by impacts.
Meteors
A meteor is a flash of light (shooting star or falling star) seen when a meteoroid, asteroid, or comet heats up in the Earth’s atmosphere. Most meteors come from meteoroids. Millions of meteors occur every day, but most come from meteoroids about the size of a grain of sand.
A fireball is a brighter-than-normal meteor. Technically, it’s a meteor brighter than any of the planets (magnitude -3 or greater, if viewed at zenith). A bolide is an especially bright fireball, especially one that explodes. Super-bright bolides are called superbolides.
Not all fireballs and bolides burn up in the atmosphere or crash to Earth. A few hit the atmosphere and leave. These meteors are called Earth-grazing fireballs.
Meteor colors depends on their chemical composition and how quickly they most through the atmosphere. Yellow meteors are usually high in sodium, orange-yellow meteors contain iron, blue-green meteors contain magnesium, violet meteors are rich in calcium, and red meteors result from superheated nitrogen and oxygen in the atmosphere. But, a single meteor streak can display multiple colors, relating to its minerals and the ionization of air.
Meteorites
Meteorites are meteoroids, asteroids, and comets that enter the atmosphere and survive to impact the surface. Relatively recently, scientists had to amend the definition of a meteorite to only include natural solid objects falling to the Earth from space. The earlier definition included any fallen object, such as fallen satellites or rocket boosters.
References
- Erickson, Jon (2003). Asteroids, Comets, and Meteorites: Cosmic Invaders of the Earth. The Living Earth. New York: Infobase. ISBN 978-0-8160-4873-1.
- McSween, Harry (1999). Meteorites and Their Parent Planets (2nd ed.). Cambridge: Cambridge University Press. ISBN 978-0521583039.
- Rubin, Alan E.; Grossman, Jeffrey N. (January 2010). “Meteorite and Meteoroid: New Comprehensive Definitions”. Meteoritics & Planetary Science. 45 (1): 114–122. doi:10.1111/j.1945-5100.2009.01009.x
- Sears, D. W. (1978). The Nature and Origin of Meteorites. New York: Oxford Univ. Press. ISBN 978-0-85274-374-4.