Meteors, Asteroids and Planet Earth

How Astronomers Identify the Many Objects in Space

by Pallav Regmi, age 13

Although there is a difference between asteroids and meteoroids, both are solid bodies in space.  A meteoroid is a small piece of space debris, usually made up of rock or iron.  This meteoroid is re-labeled a meteorite when it enters a planet’s atmosphere.  An asteroid is described as a larger, solid body of rock that orbits around a star.  

An asteroid is big enough to be seen from a distance but it is not large enough to be a planet.  Giuseppe Piazzi was the first person to discover an asteroid. He made this discovery in 1801.  

At first Piazzi believed he was looking at a comet with no tail. Of course at the time, he wasn’t really sure.  A German mathematician named Karl Friedrich Gauss calculated the orbit and discovered that the object Piazzi had found was orbiting around the Sun between Mars and Jupiter.  Piazzi named the object Ceres, which is now known to be the largest asteroid in the inner solar system.  Ceres is about 933 km in size, which is about the distance from Chicago, Illinois to Washington D.C. 

A second huge asteroid was spotted about a year after Piazzi first discovered Ceres. This asteroid is now known as Pallas.  Most asteroids that have been discovered are found in the asteroid belt between Mars and Jupiter.

Humans have noticed meteorites since the prehistoric times. But, until the 1800’s, no one really knew what they were or where they came from.  When a meteorite burns up in the atmosphere, it creates a streak of light that can be seen from Earth.  This streak of light is usually referred to as a shooting star, but its scientific name is a meteor.  

The meteorites that make this light are probably around the size of a grain of sand.  A meteorite can move at a speed of anywhere from 11 km per second to 73 km per second.  On Earth, meteors usually become visible at an altitude of about 120 km.  Meteoroids that fly fast are usually debris from comets.  Some meteoroids are slower and have highly elliptical orbits around the sun in the opposite direction.  Meteoroids can sometimes crash with spacecrafts. Meteorites usually do not survive the fall all the way to the surface of a planet like Earth.  After entering our atmosphere, a meteorite loses 95% to 99% of its weight as it descends toward Earth’s surface.  

There are many differences between asteroids, meteors, meteoroids, and meteorites.  Asteroids are large solid bodies in space that orbit a star while a meteoroid is an extremely small, solid piece of debris in space that does not have a special orbit.  Meteoroids cannot be labeled a meteorite until the piece of debris enters a planet’s atmosphere.  When the meteorite burns up and creates a streak of light in the atmosphere, it is called a meteor or more commonly known as shooting star. 

[Sources: www.freemars.org; Children’s Atlas of the Universe]

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