Related topics: stars · planets · solar system · jupiter

Coming in hot: NASA's Chandra checks habitability of exoplanets

Using NASA's Chandra X-ray Observatory and ESA's (European Space Agency's) XMM-Newton, astronomers are exploring whether nearby stars could host habitable exoplanets, based on whether they emit radiation that could destroy ...

Maybe ultra-hot Jupiters aren't so doomed after all

Ultra-hot Jupiters (UHJs) are some of the most fascinating astronomical objects in the cosmos, classified as having orbital periods of less than approximately three days with dayside temperatures exceeding 1,930°C (3,500°F), ...

Saturn-sized exoplanet isn't losing mass quickly enough

We have discovered more than 5,000 planets around other star systems. Among the veritable cosmic menagerie of exoplanets, it seems there is a real shortage of Neptune-sized planets close to their star.

Warm Jupiter exoplanet orbiting distant star detected

Astronomers report the discovery of a new warm Jupiter exoplanet orbiting a distant star in the open cluster Messier 67. The newfound extrasolar world, designated S1429 b, is almost twice as massive as Jupiter. The finding ...

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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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