* Planet: The smallest of the listed objects. Planets orbit stars.
* Star: Stars are massive balls of hot gas that produce their own light and heat. They are much larger than planets.
* Solar System: A solar system is a collection of planets, moons, asteroids, comets, and other objects that orbit a star.
* Galaxy: A galaxy is a vast collection of stars, gas, dust, and dark matter held together by gravity. Galaxies are much larger than solar systems.
* Cluster: A cluster is a group of galaxies bound together by gravity. Clusters are the largest of the listed objects.
So, the order from smallest to largest is: Planet, Star, Solar System, Galaxy, Cluster.
