Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth the mass of the Sun. Jupiter is the third-brightest natural object in the Earth’s night sky after the Moon and Venus. It has been observed since pre-historic times and is named after the Roman god Jupiter, the king of the gods, because of its observed size. Jupiter is primarily composed of hydrogen, but helium constitutes one quarter of its mass and one tenth of its volume. It likely has a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. The on-going contraction of its interior generates heat greater than the amount received from the Sun. Because of its rapid rotation, the planet’s shape is that of an oblate spheroid; it has a slight but noticeable bulge around the equator. The outer atmosphere is visibly segregated into several bands at different latitudes, with turbulence and storms along their interacting boundaries. A prominent result of this 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. The Great Red Spot is a persistent high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. Located 22 degrees south of Jupiter’s equator, it produces wind-speeds up to 432 km/h (268 mph). Observations from 1665 to 1713 are believed to be of the same storm; if this is correct, it has existed for at least 356 years. It was next observed in September 1831, with 60 recorded observations between then and 1878, when continuous observations began. There are 79 known moons of Jupiter, not counting a number of moonlets likely shed from the inner moons, and S/2003 J 24, whose orbital elements have not yet been published. All together, they form a satellite system which is called the Jovian system. The most massive of the moons are the four Galilean moons: Io; Europa; Ganymede; and Callisto, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. Much more recently, beginning in 1892, dozens of far smaller Jovian moons have been detected and have received the names of lovers (or other sexual partners) or daughters of the Roman god Jupiter or his Greek equivalent Zeus. The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 75 known moons and the rings together composing just 0.003% of the total orbiting mass. Of Jupiter’s moons, eight are regular satellites with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter’s equatorial plane. The Galilean satellites are nearly spherical in shape due to their planetary mass, and so would be considered at least dwarf planets if they were in direct orbit around the Sun. The other four regular satellites are much smaller and closer to Jupiter; these serve as sources of the dust that makes up Jupiter’s rings. The remainder of Jupiter’s moons are irregular satellites whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. These moons were probably captured by Jupiter from solar orbits. Twenty-two of the irregular satellites have not yet been officially named. Elements of this Video furnished by NASA. Full HD.