What is a meteoroid?
A meteoroid is a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom. Meteoroids travel around the Sun in a variety of orbits and with velocities ranging from ∼ 11 to ∼ 72 km/s. Sometimes they are in a collision orbit with Earth and enter our atmosphere. Most meteoroids are tiny pieces of dust.
What is a meteor?
A meteoroid is thus a particle of debris in the Solar System. The visible phenomenon due to the flight of a meteoroid through the atmosphere is called a meteor, also known as 'shooting star'. It typically occurs between altitudes of ~ 120 and ~ 80 km.
What is a meteorite?
If a meteor reaches the ground, then it is called a meteorite.
A meteorite is a solid piece of debris which has survived the passing of a meteoroid through the Earth’s atmosphere and falls on the ground. It is considerably smaller than the size of the initial meteoroid. Only large meteoroids can give rise to meteorites which are therefore quite rare.
Meteor shower definition
Most meteors can occur at any time and in any direction. They belong to what is called the sporadic meteors. Their origin is mostly related to asteroids. They constitute the bulk of meteors falling into the Earth's atmosphere.
However, there is a second population of meteors associated with dust released along the orbit of a comet. When a comet approaches the Sun, it warms up and releases dust grains along its orbit. If Earth is crossing the orbit of this comet, it passes every year at the same time into a cloud of dust particles which produces a meteor shower.
Due to a geometrical effect, all meteors belonging to a meteor shower seem to come from one point in the sky called the radiant. Each meteor shower is named after the constellation this point belongs to. For example, the radiant of the Perseids is located in the Perseus constellation.