Jupiter, the largest planet in the Solar System, has a volume equal to more than 1,000 Earths. The fifth planet from the Sun is called a gas giant because it has no solid surface, being mainly composed of hydrogen and helium. It is believed to have liquid metallic hydrogen in its interior that generates the planet's intense magnetic field.
Photo: A true colour mosaic of Jupiter taken by the Cassini probe (NASA/JPL/Space Science Institute)
The largest planet is wracked by ancient storms.
Pioneer 10 and 11 discover hazards facing the Voyager probes.
The Pioneer 10 and 11 spacecraft, launched in 1972 and 1973 respectively, survived the asteroid belt and Jupiter's radiation belt and magnetic field. These probes fed crucial information to scientists designing the Voyager 1 and 2 spacecraft.
The first detailed views of Jupiter surprise Voyager scientists.
Voyager 1, launched in 1977, sent back its first images of Jupiter in the late 1970s while it was still 50 million miles away from the planet. The gas giant's bizarre clouds and storms puzzled experts.
Prof Brian Cox demonstrates gravity’s force on other planets.
Prof Brian Cox simulates the strength of gravity on other planets through a human centrifuge in Holland.
Enjoy Astronomer Marek Kukula's guide to the Solar System.
If Jupiter were much larger it would be a star in its own right! Enjoy Astronomer Marek Kukula's eloquent guide to the Sun, the planets and the outer reaches of the Solar System.
Bad luck affects the atmospheric probe's findings.
The careful planning that went into the Galileo mission to Jupiter couldn't predict that the atmospheric probe would fall between Jupiter's clouds during its descent in 1995 and miss out on key data.
Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with mass one-thousandth of that of the Sun but is two and a half times the mass of all the other planets in the Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian or outer planets. The planet was known by astronomers of ancient times. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough to cast shadows, and making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly match Jupiter's brightness at certain points in its orbit.)
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, although helium only comprises about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other gas giants, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of 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 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere. There are also at least 67 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 flyby missions and later by the Galileo orbiter. The most recent probe to visit Jupiter was the Pluto-bound New Horizons spacecraft in late February 2007. The probe used the gravity from Jupiter to increase its speed. Future targets for exploration in the Jovian system include the possible ice-covered liquid ocean on the moon Europa.