Meteors, Meteor showers, Meteoroids and Meteorites, sounds very confusing right? They all sound similar but have different meanings. A meteoroid is a small rocky or metallic body in outer space. Most are pieces of other, larger bodies that have been broken or blasted off. Some come from comets, others from asteroids, and some even come from the Moon and other planets.When meteoroids enter Earth’s atmosphere, or that of another planet at high speed and burn up, they’re called meteors. This is also when we refer to them as “shooting stars.” Sometimes meteors can even appear brighter than Venus — that’s when we call them “fireballs.” When a meteoroid survives its trip through the atmosphere and hits the ground, it’s called a meteorite. I hope you are clear with the difference now. To know further about them, and the type of meteor showers, read ahead.
In 1961, the International Astronomical Union (IAU) defined a meteoroid as “a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom”. Meteoroids are significantly smaller than asteroids, and range in size from small grains to one-meter-wide objects.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.
Almost all meteoroids contain extraterrestrial nickel and iron. They have three main classifications: iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites. Stony meteoroids without these features are called “achondrites”, which are typically formed from extraterrestrial igneous activity; they contain little or no extraterrestrial iron.
A meteor, known colloquially as a shooting star or falling star, is the visible passage of a glowing meteoroid, micrometeoroid, comet or asteroid through Earth’s atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake. Although a meteor may seem to be a few thousand feet from the Earth, meteors typically occur in the mesosphere at altitudes from 76 to 100 km (250,000 to 330,000 ft). Millions of meteors occur in Earth’s atmosphere daily. Most meteoroids that cause meteors are about the size of a grain of sand.
A fireball is a brighter-than-usual meteor that also becomes visible when about 100 km from sea level. The International Astronomical Union (IAU) defines a fireball as “a meteor brighter than any of the planets” (apparent magnitude −4 or greater).
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. A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet or other source. The passage of Earth through cosmic debris from comets and other sources is a recurring event in many cases.
Meteor showers throughout the year:
May: Eta Aquarids
June: Arietids and Bootids
July: Southern Delta Aquarids
Each of these, except the Geminids, is caused by Earth moving through a stream of comet debris. The Geminids come from a stream of debris from the Asteroid 3200 Phaethon, which is probably a dead comet.
A meteorite is a portion of a meteoroid or asteroid that survives its passage through the atmosphere and hits the ground without being destroyed. Meteorites are sometimes, but not always, found in association with hypervelocity impact craters; during energetic collisions, the entire impactor may be vaporized, leaving no meteorites. Geologists use the term, “bolide”, in a different sense from astronomers to indicate a very large impactor. Meteorites can be very useful in studying the history of the Solar System to other planets.