Hot Jupiter
Videos
Page
Hot Jupiters are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods. The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters".
An artist's impression of a hot Jupiter orbiting close to its star.
Hot Jupiter with hidden water
Comparison of "hot Jupiter" exoplanets (artist concept). From top left to lower right: WASP-12b, Boinayel, WASP-31b, Bocaprins, HD 189733b, Puli, Ditsö̀, Banksia, HAT-P-1b and HD 209458b.
Gas giant
Videos
Page
A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranus and Neptune are really a distinct class of giant planets, being composed mainly of heavier volatile substances. For this reason, Uranus and Neptune are now often classified in the separate category of ice giants.
Jupiter photographed by New Horizons in January 2007
Saturn at equinox, photographed by Cassini in August 2009
Artist's impression of the formation of a gas giant around the star HD 100546
![A gas giant exoplanet [right] with the density of a marshmallow has been detected in orbit around a cool red dwarf star [left] by the NASA-funded NEID](https://upload.wikimedia.org/wikipedia/commons/thumb/b/b3/Artist_impression_of_ultra_fluffy_gas_giant_planet_orbiting_a_red_dwarf_star.jpg/600px-Artist_impression_of_ultra_fluffy_gas_giant_planet_orbiting_a_red_dwarf_star.jpg)
A gas giant exoplanet [right] with the density of a marshmallow has been detected in orbit around a cool red dwarf star [left] by the NASA-funded NEID radial-velocity instrument on the 3.5-meter WIYN Telescope at Kitt Peak National Observatory.