What is the order from largest to smallest: galaxy, universe, star, asteroids, planets, moons, solar system?

Let's describe them from smallest to largest. In fact the size order is not exact as there are exceptions.

An asteroid is a rocky body which lies in the asteroid belt between Mars and Jupiter. They are typically quite small object. The largest asteroid Ceres has been reclassified as a dwarf planet.

A moon is typically a rocky body which is in orbit around a planet. Some moons such as our Moon are quite large and are typically bigger than asteroid. Some moons can actually be smaller than some asteroids.

A planet is a nearly spherical body which is in orbit around the Sun. Planets are larger than moons.

A star is what planets orbit around. It is the source of light and heat. Our Sun is a star which is many times bigger than all of the planets.

A solar system is a star and all of its planets, asteroids, comets and other bodies. It is significantly bigger than a star.

A galaxy, such as our Milky Way Galaxy, is a collection of solar systems orbiting around a central core. Most galaxies have a supermassive black hole at their centres.

Galaxies also form clusters which are large scale structures.

The universe is everything. It contains billions of galaxies.

the solar system, planets, moons, asteroids, universe, and galaxy.