*Why Ceres? Ceres is important because it is the oldest known "dwarf planet"
(as currently classified by the International Astronomical Union
only missing "planet" status because it is in the asteroid belt (between the orbits of Mars and Jupiter).
Were it away from other asteroids, Ceres would be a planet outright.
Indeed, when Ceres was discovered in 1801, it was called a planet—the eighth planet, since Neptune had yet to be discovered.
Pluto is another dwarf planet in this orrery. Like Ceres, it too is a former planet.