Short answer
Asteroids are rocky or metallic bodies orbiting the Sun, generally larger than meteoroids. Meteoroids are smaller natural objects moving through space, often pieces shed by asteroids or comets. If a meteoroid enters an atmosphere, the visible streak is a meteor; surviving material on the ground is a meteorite. 1 2
Related space-rock categories largely distinguished by size and usage; a fragment of an asteroid may be a meteoroid.
On this page
At a glance
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| Question | Asteroid | Meteoroid |
|---|---|---|
| Usual size | Generally larger | Generally smaller |
| Location here | In space, orbiting the Sun | In space |
| Example | A main-belt body | A pebble-sized fragment in interplanetary space |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Asteroid. A rocky or metallic small Solar System body orbiting the Sun, typically larger than a meteoroid. 1
Meteoroid. A relatively small natural rocky or metallic object traveling through space. 2
Key differences
These labels are not separated by one universally applied size threshold in everyday NASA explanations. Origin and context matter: an asteroid collision can make smaller fragments that become meteoroids. Meteor and meteorite name events or material after atmospheric entry, not competing kinds of orbiting body. 1 2
A collision or breakup can produce fragments much smaller than the parent asteroid. Those pieces may travel through space as meteoroids. The later atmospheric names describe what happens to a fragment along its path: a luminous meteor during entry and, if material survives, a meteorite on the surface. 1 2
How to tell them apart
Start with location: if the object is still traveling in space, asteroid or meteoroid may fit; if you see a luminous atmospheric streak, call that meteor. For the space object, check the source’s stated size convention rather than assuming a strict cutoff. 1 2
Where they overlap
Both can be rock or metal left from Solar System formation, and both may orbit the Sun. A meteoroid can come from an asteroid. 1 2
Edge cases
Large meteoroids and very small asteroids make the size boundary fuzzy. Comet fragments can be meteoroids too. A bright atmospheric event does not mean the incoming object was formerly classified as a major asteroid. 1 2
Sources can draw the asteroid–meteoroid size line differently, so an exact meter value should be cited to a particular convention rather than presented as universal. A small space object may also come from a comet, which means “meteoroid” does not establish an asteroidal origin. 1 2
Why the distinction exists
The vocabulary traces a body from its space context to its encounter with an atmosphere and possible arrival at the surface. 1 2
Common misconceptions
A meteor is not a rock sitting in space; it is the atmospheric light phenomenon. A meteorite is material that reaches the ground. 1 2
Examples
A small fragment chipped from an asteroid can travel as a meteoroid, make a meteor as it enters Earth’s atmosphere and leave a meteorite if part survives. 1 2
Sources
Sources checked October 3, 2026.
- NASA Science — Asteroid Facts. Asteroid Facts.
- NASA Science — Meteors and Meteorites: Facts. Meteoroids; Meteors; Meteorites.