"Why are there so many planets?! I thought there were eight!"

There are eight planets according to the International Astronomical Union, but that is just one valid definition. The geophysical definition is the same, but removes the requirement that a planet must "clear the neighborhood around its orbit". This way, planets are defined based on their intrinsic characteristics and not their surroundings. For example, if Earth and Pluto traded places, Pluto would be a planet according to the IAU while Earth would be gravitationally dominated by Neptune, and therefore not be a planet.

If you like categorizing celestial objects based on their dynamical relationships with other objects, the IAU definition works fine! But if you're more interested in what the object is like physically, then the geophysical definition may be more useful and intuitive for you. Fortunately, using one definition doesn't negate the other!

The Table of Planets provides a way of visualizing the Solar System's geophysical planets while taking cues from the periodic table of chemical elements for presenting a large number of sciencey things at once. This way, every planet is shown on equal ground, and planets often ignored, such as the large asteroids or the giant planets' icy moons, are shown as intriguing, unique worlds of their own.

If you'd like to learn more, you can read our paper below! If you'd like to use the Table of Planets yourself, check out our downloads page!