Dwarf planets

 The universe contains unique objects that don't always fit into neat categories like stars, planets and galaxies. Dwarf planets share particular characteristics that have traditionally made them a bit harder to classify.

What are dwarf planets?

Dwarf planets are celestial objects that:

• orbit a star

• are roughly spherical

• often have many other large bodies such as comets, asteroids, or other dwarf planets near them

• As their name suggests, the main difference between a dwarf planet and a planet is size. Because they are smaller, dwarf planets lack the gravitational forces needed to pull in and accumulate all of the material found in their orbits. Each known dwarf planet in our solar system is actually smaller than Earth's Moon!

Dwarf planets in our solar system

As the authority on the naming and classification of celestial objects, the International Astronomical Union officially recognizes five dwarf planets in the solar system:

• Pluto

• Eris

• Ceres

• Makemake

• Haumea

Several dozens more are being considered for the category, and scientists estimate that hundreds or even thousands of dwarf planets may exist in the solar system.