Related topics: stars · planets · solar system · jupiter

30 years ago: Voyager 2's historic Neptune flyby

Thirty years ago, on Aug. 25, 1989, NASA's Voyager 2 spacecraft made a close flyby of Neptune, giving humanity its first close-up of our solar system's eighth planet. Marking the end of the Voyager mission's Grand Tour of ...

New space discovery sheds light on how planets form

Researchers at Dartmouth College have discovered a planet orbiting one of the brightest young stars known, according to a study published in the journal The Astrophysical Journal Letters. Aged at approximately 45 million ...

Scientist develops novel algorithm to aid search for exoplanets

Inspired by movie streaming services such as Netflix or Hulu, a Southwest Research Institute scientist developed a technique to look for stars likely to host giant, Jupiter-sized planets outside of our solar system. She developed ...

Moon maps, lunar origins and everything between

The moon's consistent appearance in the sky each night may lull earthlings into a sense of familiarity, but the moon is actually a puzzling place. It lacks an atmosphere and is bone-dry; it can hardly claim a central iron ...

Gemini Planet Imager analyzes 300 stars

Over the past four years, an instrument attached to a telescope in the Chilean Andes—known as the Gemini Planet Imager—has set its gaze on 531 stars in search of new planets. The team, led by Stanford University, is now ...

What does Uranus sound like?

Sometimes kids ask really simple questions – and parents have no idea what the answers are. When one of our colleagues was asked what it sounds like on the planet Uranus, she was stumped. And so were we! So we asked an ...

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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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