History of Solar System formation and evolution hypotheses with Uranus having a 98° tilt. The Moon being relatively large with respect to the Earth and other moons which are in irregular orbits with respect to their planet is yet another issue. It is now believed these observations are explained by events which happened after the initial formation of the Solar System. Attempts to isolate the physical source of the Sun's energy, and thus determine when and how it might ultimately run out, began in the 19th century. At that time, the prevailing scientific view on the source of the Sun's heat was that it was generated by gravitational
Moons of Saturn These moons are coated with dusty material that has smoothed out their surfaces. These moons all orbit beyond the E Ring. They are: Irregular moons are small satellites with large-radii, inclined, and frequently retrograde orbits, believed to have been acquired by the parent planet through a capture process. They often occur as collisional families or groups. The precise size as well as albedo of the irregular moons are not known for sure because the moons are very small to be resolved by a telescope, although the latter is usually assumed to be quite low—around 6% (albedo of Phoebe) or less.