Ice giant in mass. In 1952, science fiction writer James Blish coined the term "gas giant" and it was used to refer to the large non-terrestrial planets of the Solar System. However, in the 1990s, the compositions of Uranus and Neptune were discovered to be significantly different from those of Jupiter and Saturn. They are primarily composed of elements heavier than hydrogen and helium, constituting a separate type of giant planet altogether. Because during their formation Uranus and Neptune incorporated their material as either ices or gas trapped in water ice, the term "ice giant" came into use. Modelling the formation of
Formation and evolution of the Solar System million years, the young Sun's solar wind would have cleared away all the gas and dust in the protoplanetary disc, blowing it into interstellar space, thus ending the growth of the planets. The planets were originally thought to have formed in or near their current orbits. From that a minimum mass of the nebula i.e. the protoplanetary disc, was derived that was necessary to form the planets - the minimum mass solar nebula. It was derived that the nebula mass must have exceeded 3585 times that of the Earth. However, this has been questioned during the last 20 years. Currently,