From the list you provided, the item that can be excluded as it is not an object in the solar system is constellation.
Here's a breakdown:
- Planet: Objects in the solar system (e.g., Earth, Mars).
- Asteroid belt: An area in the solar system containing numerous asteroids, specifically located between the orbits of Mars and Jupiter.
- Sun: The star at the center of our solar system.
- Constellation: A grouping of stars that may be located in different parts of space and are not specific to our solar system.
Thus, the constellation is the correct answer to exclude.