Related topics: planets · solar system · jupiter

Unknown structure in galaxy revealed by high contrast imaging

As a result of achieving high imaging dynamic range, a team of astronomers in Japan has discovered for the first time a faint radio emission covering a giant galaxy with an energetic black hole at its center. The radio emission ...

Even stars doomed to die as supernovae can have planets

Ninety percent of all exoplanets discovered to date (there are now more than 5,000 of them) orbit around stars the same size or smaller than our sun. Giant stars seem to lack planetary companions, and this fact has serious ...

From dust to planet: How gas giants form

Gas giants are made of a massive solid core surrounded by an even larger mass of helium and hydrogen. But even though these planets are quite common in the Universe, scientists still don't fully understand how they form. ...

Astronomers discover more than 300 possible new exoplanets

UCLA astronomers have identified 366 new exoplanets, thanks in large part to an algorithm developed by a UCLA postdoctoral scholar. Among their most noteworthy findings is a planetary system that comprises a star and at least ...

Image: Hubble spots dark star-hatching frEGGs

This image shows knots of cold, dense interstellar gas where new stars are forming. These Free-floating Evaporating Gaseous Globules (frEGGs) were first seen in Hubble's famous 1995 image of the Eagle Nebula. Because these ...

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Gas giant

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.

Gas giants can be subdivided into different types. The "traditional" gas giants, Jupiter and Saturn, are composed primarily of hydrogen and helium. Uranus and Neptune are sometimes considered a separate subclass called ice giants, as they are mostly composed of water, ammonia, and methane; the hydrogen and helium in Uranus and Neptune is mostly in the outermost region. Among extrasolar planets, Hot Jupiters are gas giants that orbit very close to their stars and thus have a very high surface temperature; perhaps due to the relative ease of detecting them, Hot Jupiters are currently the most common form of extrasolar planet known.

Gas giants are commonly described as lacking a solid surface, although a more accurate description is to say that they lack a clearly-defined surface. Although they have rocky or metallic cores - in fact, such a core is thought to be required for a gas giant to form - the majority of the mass of Jupiter and Saturn is hydrogen and helium. In the planet's upper layers, these elements are gaseous, as they are on Earth, but further down in the planet's interior, they become compressed into liquids or solids, which become denser toward the core. Similarly, although the majority of Uranus and Neptune is icy, the extreme heat and pressure of these planets' interiors put the ices into less familiar physical states. Therefore, one cannot "land on" gas giants in a traditional sense. Terms such as diameter, surface area, volume, surface temperature, and surface density may refer only to the outermost layer visible from space.

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