News about space rocks mixes these words constantly. They mean different things, and once you know the difference, headlines about Apophis make a lot more sense.
A rocky or metallic body that orbits the Sun, smaller than a planet. Most live in the main asteroid belt between Mars and Jupiter. Sizes range from a few meters to hundreds of kilometers. Apophis is an asteroid, about 340 meters wide.
A body made mostly of ice, dust and rock, often called a "dirty snowball." When a comet gets close to the Sun, its ice vaporizes and creates a glowing cloud (coma) and a tail that always points away from the Sun. Comets usually come from the cold outer solar system. Apophis has no tail, so it is not a comet.
A small piece of rock or metal in space, from the size of a grain of sand up to about a meter. Meteoroids are often fragments broken off from asteroids or comets.
The streak of light you see when a meteoroid enters Earth's atmosphere and burns up from friction. This is what people call a "shooting star." A meteor is the light, not the rock.
A meteor that is exceptionally bright, brighter than the planet Venus, is called a fireball. If it explodes in the atmosphere, it is sometimes called a bolide.
A piece that survives the trip through the atmosphere and lands on Earth's surface. Meteorites are valuable to scientists because they are samples of the early solar system.
| Term | Where is it? | What is it? |
|---|---|---|
| Asteroid | Orbiting the Sun | Rocky/metal body, meters to hundreds of km |
| Comet | Orbiting the Sun | Ice and dust, grows a tail near the Sun |
| Meteoroid | In space | Small rock, grain to about a meter |
| Meteor | In the atmosphere | The streak of light |
| Meteorite | On the ground | The surviving piece |
Now you can read the news with confidence. Next, learn what makes Apophis special or how it compares to the dinosaur asteroid.