In general, the term “gas giant – gas giant planets” was coined in 1952 by James Blish. A gas giant is a large planet that is not composed mainly of solid matter. In contrast, most planets consist of solid material in their core but other components/elements within the surface are above critical point. In such cases, there is often no clear distinction between liquids and gases. This often leads to confusion regarding terms used. For example, scientists use “gas”, “rock”, and “ice” to describe elements beyond earth. In the solar system, helium and hydrogen are “gases” while ammonia, methane, and water are “ices”. Gas giants are also known as Jovian planets (named after Roman god- Jupiter) as they are highly similar to planet Jupiter.
Scientists take on the task to identify gas giant planets and have come to a conclusion that there are four Jovian planets in our solar system- Uranus, Neptune, Saturn, and Jupiter. These planets are massive in size and have a thick atmosphere. Their core composed of small solid matter. Traditional Jovian planets would be Jupiter and Saturn as they are made up of helium and hydrogen gases. Neptune and Uranus are sometimes known as “ice giants” as they compose of ammonia, methane, and water. As for extra-solar planets (planets beyond the solar system), Hot Jupiters are known to be gas giant – gas giant planets. In the upper layer of Jovian planets, the elements are gaseous but compressed into liquids/solids as they move closer to the core. It’s interesting to note that though Uranus and Neptune are known as “icy planets”, the extreme pressure and heat emitted from the interior layers creates a unique condition within the surface. Technically, landing on such planet is quite impossible, as the planet’s gravity might crush whatever that enters its system.
To identify gas giant planets, scientists have to consider multiple factors. The uniqueness of four planets- Uranus, Neptune, Saturn, and Jupiter classifies it into that category.