History of Solar System formation and evolution hypotheses is captured by the Sun and planets form from it. In this there were 6 original planets, corresponding to 6 point-masses in the filament, with planets A and B, the 2 innermost, colliding, the former at twice the mass of Neptune, and ejecting out of the Solar System, and the latter at 1/3 the mass of Uranus, and splitting into Earth and Venus. Mars and the Moon are former moons of A. Mercury is either a fragment of B or an escaped moon of A. The collision also produced the asteroid belt and the comets. T.J.J. See was an American
Moons of Uranus spheroid are highlighted in light blue and bolded. Irregular moons with retrograde orbits are shown in dark grey. Margaret, the only known irregular moon of Uranus with a prograde orbit, is shown in light grey. "Sources:" NASA/NSSDC, Sheppard, et al. 2005. For the recently discovered outer irregular moons (Francisco through Ferdinand) the most accurate orbital data can be generated with the Natural Satellites Ephemeris Service. The irregulars are significantly perturbed by the Sun. Moons of Uranus Uranus is the seventh planet of the Solar System; it has 27 known moons, all of which are named after characters from the works