For centuries since the Sun was declared the center of the solar system in the 16th century, society held the belief that any object orbiting the bright star would be considered a planet. From Mercury to Pluto, every celestial body deemed large enough was put in this category.
But over time, this categorization became confusing, especially as it became clear that not all “planets” are alike. Astronomy has changed significantly since then, and even Pluto has seen its status as a planet demoted to a mere dwarf planet. But what exactly is that? And what does it take for a planet to be put in this category? Click through this gallery to find out.