Meteoroids

Meteoroids are small rocky or metallic bodies in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects.

Meteoroid_meteor_meteorite


Objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars. 

A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeorite is such a particle that survives passage through the Earth's atmosphere and reaches the Earth's surface.


When a meteoroid, comet, or asteroid enters Earth's atmosphere at a speed typically in excess of 20 km/s (72,000 km/h; 45,000 mph), aerodynamic heating of that object produces a streak of light, both from the glowing object and the trail of glowing particles that it leaves in its wake. 


Shooting stars aka meteors

This phenomenon is called a meteor or "shooting star". A series of many meteors appearing seconds or minutes apart and appearing to originate from the same fixed point in the sky is called a meteor shower. If that object withstands ablation from its passage through the atmosphere as a meteor and impacts with the ground, it is then called a meteorite.

Leonid_Meteor

A meteor of the Leonid meteor shower. The photograph shows the meteor, afterglow, and wake as distinct components. image: Navicore/wikipedia

An estimated 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earth's atmosphere each year.


See also asteroid and meteoroid impacts to discover their effects


source adapted from: Meteoroid. (2017, May 30). In Wikipedia, The Free Encyclopedia. Retrieved 10:41, June 8, 2017, from https://en.wikipedia.org/w/index.php?title=Meteoroid&oldid=783008168