![](https://static.wixstatic.com/media/b38043_11b21bd5f17d4522a1100c323a191878~mv2.jpg/v1/fill/w_1900,h_1723,al_c,q_90,enc_auto/b38043_11b21bd5f17d4522a1100c323a191878~mv2.jpg)
JUPITER
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined. Jupiter is one of the brightest objects visible to the naked eye in the night sky and has been known to ancient civilizations since before recorded history. It is named after the Roman god Jupiter. When viewed from Earth, Jupiter can be bright enough for its reflected light to cast visible shadows and is on average the third-brightest natural object in the night sky after the Moon and Venus.
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. 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, 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. Jupiter has 79 known moons including the four large Galilean moons discovered by Galileo Galileo in 1610. Ganymede, the largest of these, has a diameter greater than that of the planet Mercury.
Pioneer 10 was the first spacecraft to visit Jupiter, making its closest approach to the planet on December 4, 1973; Pioneer 10 identified plasma in Jupiter's magnetic field and also found that Jupiter's magnetic tail was nearly 800 million kilometres long, covering the entire distance to Saturn. Jupiter has been explored on a number of occasions by robotic spacecraft, beginning with the Pioneer and Voyager flyby missions from 1973 to 1979, and later by the Galileo orbiter, which arrived at Jupiter in 1995. In late February 2007, Jupiter was visited by the New Horizons probe, which used Jupiter's gravity to increase its speed and bend its trajectory en route to Pluto. The latest probe to visit the planet is Juno, which entered into orbit around Jupiter on July 4, 2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa.
INTERNAL STRUCTURE
Jupiter was expected to either consist of a dense core, a surrounding layer of liquid metallic hydrogen (with some helium) extending outward to about 78% of the radius of the planet, and an outer atmosphere consisting predominantly of molecular hydrogen, or perhaps to have no core at all, consisting instead of denser and denser fluid (predominantly molecular and metallic hydrogen) all the way to the centre, depending on whether the planet accreted first as a solid body or collapsed directly from the gaseous protoplanetary disk. However, the Juno mission, which arrived in July 2016, found that Jupiter has a very diffuse core, mixed into the mantle. A possible cause is an impact from a planet of about ten Earth masses a few million years after Jupiter's formation, which would have disrupted an originally solid Jovian core.
Above the layer of metallic hydrogen lies a transparent interior atmosphere of hydrogen. At this depth, the pressure and temperature are above hydrogen's critical pressure of 1.2858 MPa and a critical temperature of only 32.938 K. In this state, there are no distinct liquid and gas phases—hydrogen is said to be in a supercritical fluid state. It is convenient to treat hydrogen as gas extending downward from the cloud layer to a depth of about 1,000 km, and as a liquid in deeper layers. Physically, there is no clear boundary—the gas smoothly becomes hotter and denser as one descends. Rain-like droplets of helium and neon precipitate downward through the lower atmosphere, depleting the abundance of these elements in the upper atmosphere. Rainfalls of extraterrestrial diamonds have been suggested to occur, as well as on Saturn and the ice giants Uranus and Neptune.
The temperature and pressure inside Jupiter increase steadily inward, due to the Kelvin–Helmholtz mechanism. At the pressure level of 10 bars (1 MPa), the temperature is around 340 K (67 °C; 152 °F). At the phase transition region where hydrogen—heated beyond its critical point—becomes metallic, it is calculated the temperature is 10,000 K (9,700 °C; 17,500 °F) and the pressure is 200 GPA. The temperature at the core boundary is estimated to be 36,000 K (35,700 °C; 64,300 °F) and the interior pressure is roughly 3,000–4,500 GPA.
Prior models of Jupiter's interior suggested a core radius of 0.08 to 0.16 of Jupiter's overall radius. Early results from the Juno mission suggest the core may be larger and more diffuse with a radius from 0.3 to 0.5 of the planetary radius.
MOONS OF JUPITER
Jupiter has 67 confirmed moons orbiting the planet. These moons are separated into three groups:
-
Inner moons. These orbits the closest to Jupiter and are sometimes called the Amalthea group. The names of the inner moons of Jupiter are Metis, Adrastea, Amalthea, and Thebe.
-
Galilean moons. These are largest of Jupiter’s moons and were discovered by Galileo in 1610 – Io, Europa, Ganymede and Callisto.
-
Outer moons. These moons are much smaller and further away from Jupiter. They also have irregular, elliptical orbit paths and many are captured asteroids.
JUPITERITE FACTS
The first recorded sighting of Jupiter was by the ancient Babylonians in around 7th or 8th BC. It is named for Jupiter, the king of the Roman gods and god of the Sky. The Greek equivalent is Zeus, the god of thunder. For the Mesopotamians, he was the god Marduk and patron of the city of Babylon. Germanic tribes saw the planet as Donar, also known as Thor.
When Galileo discovered the four moons of Jupiter in 1610 this was the first proof of celestial bodies orbiting something other than Earth. The discovery also provided further evidence of Copernicus’ Sun-centred solar system model.
Jupiter has the shortest day of the eight planets. The planet rotates very Jupiter rotates very quickly, turning on its axis once every 9 hours and 55 minutes. This rapid rotation is also what causes the flattening effect of the planet, which is why it has an oblate shape.
One orbit of the Sun takes Jupiter 11.86 Earth years. This means that when viewed from Earth, the planet appears to move very slowly in the sky. It takes months for Jupiter to move from one constellation to the next.
Jupiter has a faint ring system around it. Its ring is mostly comprised of dust particles from some of Jupiter’s moons during impacts from comets and asteroids. The ring system begins about 92,000 km above Jupiter’s clouds and reaches more than 225,000 k from the planet. The rings are somewhere between 2,000-12,500 km thick.
Jupiter has at least 67 moons in satellite around the planet. This includes the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610.
The largest of Jupiter’s moons, Ganymede is the largest moon in the solar system. The moons are sometimes called the Jovian satellites and the largest of them are Ganymede, Callisto, Io and Europa. Ganymede is larger than the planet Mercury with a diameter of around 5,268 km.
Jupiter has a very strong magnetic field. This is around 14 times stronger than the magnetic field found on Earth – the largest of any planet in the solar system.
Jupiter is the fourth brightest object in our solar system. After the Sun, the Moon and Venus, Jupiter is the brightest and is one of five planets which can be seen by the naked eye from Earth.
Jupiter is the only planet that has a centre of mass with the Sun that lies outside the volume of the Sun, though by only 7% of the Sun’s radius.
Jupiter has a very unique cloud layer. The upper atmosphere of the planet is divided into zones and cloud belts which are made of ammonia crystals, sulfur and a mixture of these two compounds.
Eight spacecraft have visited Jupiter so far. Those are Pioneer 10 and 11, Voyager 1 and 2, Galileo, Cassini, Ulysses and the New Horizons mission. Another mission, Juno, is set to arrive at Jupiter sometime around July 2016. There are also plans for future missions to focus on the Jovian moons of Jupiter – Europa, Ganymede and Callisto – and their possible subsurface oceans.
Jupiter does not experience seasons like other planets such as Earth and Mars. This is because the axis is only tilted by 3.13 degrees.
Jupiter’s Great Red Spot is an enormous storm that has been raging for over 300 years. This storm is so wide that three Earth’s would fit inside of it.
If Jupiter had become 80 times more massive, nuclear fusion would have occurred in its core. Had that happened, it would have become a star instead of a planet.