Here's why:

* Rocky object: Asteroids are primarily composed of rock and metal.

* Irregularly shaped body: Unlike planets, which are generally spherical, asteroids have irregular shapes due to their smaller size and lack of sufficient gravity to pull themselves into a sphere.

* Planetary material: Asteroids are remnants of the early solar system's formation, containing the same basic building blocks as planets.

* Orbits the Sun: Like planets, asteroids are bound by the Sun's gravity and follow elliptical orbits around it.