Phaeton is a hypothetical planet that was proposed in the 18th century by the French astronomer, Jean Jacques d'Ortous de Mairan. The idea was based on a series of observations of a supposed planetary body that was thought to be responsible for the gravitational perturbations of other planets in our solar system.
According to the hypothesis, Phaeton was thought to have orbited the Sun between Mars and Jupiter, in the same region where the asteroid belt is located today. It was believed to have been destroyed in a catastrophic collision with another celestial body, resulting in the formation of the asteroid belt.
While the concept of Phaeton as a hypothetical planet was once widely accepted, it has since been largely discredited by modern astronomers. The gravitational perturbations that were originally attributed to Phaeton have been found to be caused by other celestial bodies, and there is no direct evidence to support the existence of a planet in the asteroid belt. Nonetheless, the idea of Phaeton continues to be of historical interest and has contributed to our understanding of the evolution of the solar system.