Phaeton (hypothetical planet)

Phaeton (or Phaëton, less often Phaethon) is the hypothetical planet posited to have existed between the orbits of Mars and Jupiter whose destruction supposedly led to the formation of the asteroid belt. The hypothetical planet was named for Phaethon, the son of the sun god Helios in Greek mythology, who attempted to drive his father's solar chariot for a day with disastrous results and was ultimately destroyed by Zeus.

The asteroid 3200 Phaethon, sometimes incorrectly spelled Phaeton, is a Mercury-, Venus-, Earth-, and Mars-orbit crossing Apollo asteroid with unusual properties.

According to the discredited Titius–Bode law, a planet was believed to exist between Mars and Jupiter. After observing the discoveries made by the German astronomer and professor Johann Daniel Titius (1729–1796), Johann Elert Bode himself urged a search for the fifth planet. When Ceres, the largest of the asteroids in the asteroid belt (now considered a dwarf planet), was serendipitously discovered in 1801 by the Italian Giuseppe Piazzi and found to match the predicted position of the fifth planet, many believed it was the missing planet. However, in 1802 astronomer Heinrich Wilhelm Matthäus Olbers discovered and named another object in the same general orbit as Ceres, the asteroid Pallas.

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