Meteor
A meteor is the streak of light seen when a small piece of space rock burns up as it enters Earth's atmosphere, often called a shooting star.
Definition
A meteor is the bright streak you see when a small piece of rock or dust from space hits Earth's air and burns up; people call them shooting stars, but they are not stars, and most are caused by bits no bigger than a sand grain. The glowing trail forms when a meteoroid enters the atmosphere at $11$ to $72\ \text{km/s}$ and friction and compression heat it and the surrounding air at altitudes of about $80$ to $120\ \text{km}$, and a meteor shower occurs when Earth passes through debris strewn along a comet's orbit. The light comes mainly from ablation: the meteoroid's surface vaporizes and its atoms collide with air molecules, exciting emission lines of sodium, magnesium, iron, and atmospheric nitrogen and oxygen. Kinetic energy per unit mass at $30\ \text{km/s}$ is about $4.5 \times 10^8\ \text{J/kg}$, roughly $100$ times that of TNT, which is why milligram grains produce visible streaks; meteors brighter than magnitude $-4$ are fireballs, and shower meteors share a radiant because their parallel paths converge in perspective.
Example
During the Perseid shower, peaking around August 12 when Earth crosses the trail of comet Swift-Tuttle, a dark-sky observer after midnight may see a meteor every minute or two, all seeming to radiate from Perseus. Earth's orbital speed is about $30\ \text{km/s}$, so a meteoroid meeting Earth head-on arrives at up to $72\ \text{km/s}$ while one catching up from behind enters at only about $11\ \text{km/s}$, Earth's escape velocity, which is why meteor rates climb after midnight when the observer faces Earth's direction of travel.
Key Insight
A meteor burns $80$ to $100$ kilometers overhead, and the rock itself is tiny; the streak looks big because the air around it glows. Three words mark three stages: a meteoroid is the rock in space, a meteor is the streak in the sky, and a meteorite is the piece that reaches the ground, and most meteoroids never become meteorites. Roughly $40$ to $100$ tonnes of meteoroid material enters the atmosphere every day, nearly all as dust, so the solar system is still gently raining on us.