A meteoroid is a relatively small (sand- to boulder-sized) fragment of debris in the Solar System. When entering a planet's atmosphere, the meteoroid heats up and partially or completely vaporizes. The gas along the path of the meteoroid becomes ionized and glows. The trail of glowing vapor is called a meteor, or a shooting star. If any portion of the meteoroid survives to reach the ground, it is then referred to as a meteorite.