This cheat sheet explains the small rocky and icy bodies that move through the Solar System, including asteroids, comets, meteoroids, meteors, and meteorites. Students need these terms because they are easy to mix up, but each one describes a different object or event. The sheet also helps connect what we see in the night sky to where these objects come from and how they move.
Key Facts
- An asteroid is a small rocky or metallic body that orbits the Sun, and most asteroids are found in the asteroid belt between Mars and Jupiter.
- A comet is a small icy body that orbits the Sun and can form a glowing coma and tail when solar heating turns ice into gas.
- A meteoroid is a small piece of rock or metal in space, a meteor is the bright streak it makes in the atmosphere, and a meteorite is any piece that reaches the ground.
- Comet tails point generally away from the Sun because sunlight and the solar wind push gas and dust outward.
- Orbital speed depends on distance from the Sun, so objects usually move faster when closer to the Sun and slower when farther away.
- Average speed can be found with speed = distance / time when comparing how far a small body travels over a measured time.
- Impact risk increases when an object has a path that crosses Earth’s orbit and is large enough to survive entry through the atmosphere.
- Meteor showers happen when Earth passes through dust left behind by a comet, causing many meteors to appear from the same region of the sky.
Vocabulary
- Asteroid
- A small rocky or metallic object that orbits the Sun, usually smaller than a planet and often found in the asteroid belt.
- Comet
- A small icy object that orbits the Sun and may develop a glowing coma and tail when it warms up.
- Meteoroid
- A small rock or metal fragment traveling through space before it enters a planet’s atmosphere.
- Meteor
- The bright streak of light produced when a meteoroid burns up while moving through a planet’s atmosphere.
- Meteorite
- A piece of a meteoroid or asteroid that survives its trip through the atmosphere and lands on a planet or moon.
- Orbit
- The curved path an object follows around a star, planet, or moon because of gravity.
Common Mistakes to Avoid
- Calling every bright streak a meteorite is wrong because the streak in the sky is a meteor, while a meteorite is the piece that reaches the ground.
- Saying comets are just dirty asteroids is wrong because comets contain much more ice and can form comas and tails when heated by the Sun.
- Drawing a comet tail behind its path is wrong because the tail points generally away from the Sun, not always opposite the direction of motion.
- Thinking the asteroid belt is crowded like a movie scene is wrong because asteroids are usually separated by very large distances.
- Assuming all meteoroids hit Earth is wrong because many miss Earth, and many that enter the atmosphere burn up before reaching the ground.
Practice Questions
- 1 A meteoroid travels 90,000 kilometers in 2 hours. What is its average speed in kilometers per hour?
- 2 A comet leaves dust along its orbit, and Earth crosses that dust trail once each year. What sky event can this produce?
- 3 A rock from space enters Earth’s atmosphere, creates a bright streak, and a small piece lands in a field. Name the object at each stage: before entry, streak in the sky, and piece on the ground.
- 4 Explain why a comet’s tail points generally away from the Sun, even if the comet is moving toward the Sun.