A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in our Solar System: Jupiter, Saturn, Uranus, and Neptune. Many extrasolar gas giants have been identified orbiting other stars.
Planets above 10 Earth masses are termed giant planets. Lower-mass gassy planets are sometimes called “gas dwarfs”.
Jupiter’s three red spots the largest of which is called the ‘Great Red Spot’
A gas giant is a massive planet with a thick atmosphere and a dense molten core. The “traditional” gas giants, Jupiter and Saturn, are composed primarily of hydrogen and helium. Uranus and Neptune are sometimes called ice giants, as they are mostly composed of water, ammonia, and methane molten ices. Among extrasolar planets, Hot Jupiters are gas giants that orbit very close to their stars and thus have a very high surface temperature. Hot Jupiters are currently the most common form of extrasolar planet known, perhaps due to the relative ease of detecting them.
Gas giants are commonly said to lack solid surfaces, but it is closer to the truth to say that they lack surfaces altogether since the gases that make them up simply become thinner and thinner with increasing distance from the planets’ centres, eventually becoming indistinguishable from the interstellar medium. Therefore landing on a gas giant may or may not be possible, depending on the size and composition of its core.
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