The small body that circles the sun with a highly elliptical orbit is a comet.

Here's why:

* Highly Elliptical Orbit: Comets have very elongated orbits that take them far out from the sun and then bring them very close. This is unlike the more circular orbits of planets.

* Small Size: Comets are relatively small celestial bodies, often made of ice, dust, and rock.

* Tail: When a comet comes close to the sun, the heat causes its ice to sublimate (turn directly into gas), creating a long tail of dust and gas that points away from the sun.

Let me know if you have any other questions!