Jupiter

Jupiter (IPA: /ˈdʒu.pɨ.tɚ/) is the fifth planet from the Sun and the largest planet within the solar system. It is two and a half times as massive as all of the other planets in our solar system combined. Jupiter, along with Saturn, Uranus and Neptune, is classified as a gas giant. Together, these four planets are sometimes referred to as the Jovian planets. Jovian is the adjectival form of Jupiter; the Greek equivalent Zeus supplies the root zeno-, used to form some Jupiter-related words, such as zenographic.^[5]

When viewed from Earth, Jupiter can reach an apparent magnitude of −2.8, making it the fourth brightest object in the night sky. The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. The Romans named it after Jupiter (Latin: Iuppiter, Iūpiter), the principal God of Roman mythology, whose name comes from the Proto-Indo-European vocative form *dyeu ph₂ter.^[6]

The planet Jupiter is primarily composed of hydrogen with only a small proportion of helium; it may also have a rocky core of heavier elements. Because of its rapid rotation the planet is an oblate spheroid (it possesses a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the seventeenth century. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 63 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. Ganymede, the largest of these moons, has a diameter greater than that of the planet Mercury.

Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager fly-by missions and later by the Galileo orbiter. Future targets for exploration include the possible ice-covered liquid ocean on the Jovian moon Europa.