The ranking of celestial bodies in terms of size is commonly referred to as the celestial size hierarchy.

In the celestial size hierarchy, the largest celestial object is the universe itself, followed by galaxies, galactic clusters, superclusters, and so on. Within galaxies, there are stars, which are ranked from smallest to largest as white dwarfs, main-sequence stars, red giants, and supergiants.

Earth's moon, as a natural satellite of the Earth, is the fifth largest moon in the solar system. Ganymede, the largest moon of Jupiter, is the largest moon in the solar system, followed by Titan, the largest moon of Saturn.

Planets are ranked from smallest to largest as Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn, and Jupiter. Pluto, which was once classified as the ninth planet, has since been reclassified as a dwarf planet.

Asteroids, which are small, rocky bodies that orbit the sun, are ranked by size from smallest to largest. The largest known asteroid is Ceres, which is also classified as a dwarf planet.

Comets are also ranked by size, with the largest known comet being Comet Hale-Bopp, which was visible to the naked eye in 1997.

In conclusion, the celestial size hierarchy is a ranking of celestial bodies by size, with the universe being the largest and asteroids and comets being some of the smallest. Understanding the size and hierarchy of celestial bodies is an important aspect of studying and understanding our universe.