Astronomy - Planet Jupiter
Mass: 1.90 X 1027 kg (317.9 Earths)
Radius (equatorial): 71 492 km
Mean density: 1.33 g cm3
Distance from Sun: 778 330 000 km
Rotational period: 0.4135 days
Orbital Period: 4332.71 days
Escape velocity: 59.56 km s-1
Apparent magnitude: -2.70
Surface temperature: -121°C (cloud)
Atmospheric composition: hydrogen (90%), helium (10%)
Number of statellite: 16 (Europa, Ganymede, Callisto, Io etc.)
Jupiter is the largest planet and is the fourth brightest object in the sky, after the Sun, the Moon and Venus. Its volume can fit in more than one thousand Earths and contains more matter than all of the other planets combined.
Jupiter's magnetosphere, measured by the Cassini spacecrsft is found to extend far into space, with a distance equivalent to 30 times the radius of the planet. If its magnetosphere is visible from Earth, it would appear five times as large as the full moon. Unlike Saturn, Jupiter has also a ring system but is much thinner and very faint. It was only discovered when Voyager 1 approached the planet in 1979.
One can only speculate the structure of the planet. Its atmosphere is very thick and deep. The interior pressure may reach 100 millions times the pressure on Earth's surface. Just like the Sun, it is composed of mainly hydrogen and helium. Jupiter's weather is highly dynamic. Strips of latitudinal bands and turbulance clouds are clearly visible even with a small telescope. The charactristic red spot (The Giant Red Spot) is in fact a complex strom, moving in a counter-clockwise direction,
has been raging for hundreds of years. The first direct measurement of its upper atmosphere was first carried out by the Galileo Probe in July 1995. The probe managed to penetrate about 200 km before it was crushed by the atmosphere.
Jupiter has 16 known moons. The four largest moons (named in order of increasing size: Europa, Io, Callisto and Ganymede) were discovered by Galileo Galilei in 1610 and are subsequently known as the Galilean satellites. Apart from the 16 named moons, recently 23 more have been discovered but not yet been named.
Portrait of Jovian system, showing the Giant Red Spot and four largest moon (from top to bottom): Io, Europa, Genymede and Callisto. The smallest planet, Europa, is roughly the size of the Earth's moon. Very strong winds blows in the red spot at about 400 km per hour and the size is several times larger than Earth.
A mosaic of four images taken by Galileo spacecraft (at angle of 0.5 degree above the ring plane) showing Jupiter's ring. The ring brightness is due to light scattering by micrometer sized particles.
To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the faintest are purple.
Credit: Cornell University/JPL/NASA
Voyager 1 - Flyby mission to Jupiter.
Voyager 2 - Flyby mission to Jupiter. Discovered volcanic plume above the surface of Io.
Galileo Mission - Enduring mission to Jupiter. Due to running out of propellant, the spacecraft is scheduled to crushed into Jupiter on September 2003.
Europa Orbiter - Possible future mission to Europa to study surface ice.