Мұзды алып планеталар

Giant planet primarily consisting of compounds with freezing points exceeding 100°K
the type of planet

An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two ice giants in the Solar System: Uranus and Neptune. In astrophysics and planetary science the term "ice" refers to volatile chemical compounds with freezing points above about 100 K, such as water, ammonia, or methane, with freezing points of 273 K (0°C), 195 K (−78°C), and 91 K (−182°C), respectively (see Volatiles). In the 1990s, it was determined that Uranus and Neptune were a distinct class of giant planet, separate from the other giant planets, Jupiter and Saturn, which are gas giants predominantly composed of hydrogen and helium. As such, Neptune and Uranus are now referred to as ice giants. Lacking well defined solid surfaces, they are primarily composed of gases and liquids. Their constituent compounds were solids when they were primarily incorporated into the planets during their formation, either directly in the form of ice or trapped in water ice. Today, very little of the water in Uranus and Neptune remains in the form of ice. Instead, water primarily exists as supercritical fluid at the temperatures and pressures within them. and it was used to refer to the large non terrestrial planets of the Solar System. However, since the late 1940s the compositions of Uranus and Neptune have been understood to be significantly different from those of Jupiter and Saturn. They are primarily composed of elements heavier than hydrogen and helium, forming a separate type of giant planet altogether. Because during their formation Uranus and Neptune incorporated their material as either ice or gas trapped in water ice, the term ice giant came into use. but the earliest scientific usage of the terminology was likely by Dunne & Burgess (1978) in a NASA report.

Modelling the formation of terrestrial and gas giants is relatively straightforward and uncontroversial. The terrestrial planets of the Solar System are widely understood to have formed through collisional accumulation of planetesimals within the protoplanetary disk. The gas giants—Jupiter, Saturn, and their extrasolar counterpart planets—are thought to have formed solid cores of around 10 Earth masses through the same process, while accreting gaseous envelopes from the surrounding solar nebula over the course of a few to several million years (Ma), although alternative models of core formation based on pebble accretion have recently been proposed. Some extrasolar giant planets may instead have formed via gravitational disk instabilities.