Jupiter, also known as the Wood Star, is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with a mass that is one-thousandth that of the Sun but two and a half times the total mass of all the other planets in the Solar System combined.
Jupiter is classified as a gas giant along with Saturn (while Uranus and Neptune are classified as ice giants).
Jupiter is primarily composed of hydrogen and helium, making up about a quarter of its mass, although helium only constitutes one-tenth of the number of molecules.
Jupiter is the largest planet in the Solar System.
Structure of Jupiter
Jupiter primarily contains matter in gaseous and liquid states. It is the largest gas giant in the Solar System, with a diameter of 142,984 km at the equator. Its average density is 1.326 g/cm³, and it has the highest density among the four gas giants. However, this density is lower than that of any rocky planets.
The upper atmosphere of Jupiter contains about 88–92% hydrogen and 8–12% helium by volume or molecular ratio of gases. Since a helium atom has a mass four times that of a hydrogen atom, this composition changes when described in terms of mass distribution among different elements. Thus, the planet’s atmosphere contains approximately 75% hydrogen and 24% helium by mass, with about 1% made up of other elements.
The mass of Jupiter is about 2.5 times the total mass of all other planets in the Solar System.
Atmosphere of Jupiter
Jupiter also has the largest atmosphere in the Solar System, extending over 5,000 km in height. Since Jupiter lacks a solid surface, the base of its atmosphere is considered to be at a pressure of 10 bar, ten times the atmospheric pressure at the surface of Earth.
Clouds on Jupiter
Jupiter is permanently covered by layers of clouds containing ammonia crystals and possibly ammonium hydrogen sulfide.
The Great Red Spot on Jupiter
The most famous feature of Jupiter is probably the Great Red Spot, a storm that rotates in the opposite direction of Jupiter’s rotation and has a diameter often larger than Earth, located at 22° South latitude below the equator. It has existed since at least 1831, and possibly since 1665.
Image of the Great Red Spot and surrounding areas taken by Voyager 1 on February 25, 1979, when the spacecraft was 9.2 million km from the planet.
Jupiter’s Rings
Jupiter has a faint planetary ring system consisting of three main rings: the innermost ring, also known as the halo, the relatively bright main ring, and the outermost thin ring. The material composition of these rings is primarily dust rather than icy particles like those found in Saturn’s rings.
Magnetic Field of Jupiter
Jupiter’s magnetic field is 14 times stronger than Earth’s magnetic field, making it the largest magnetic field in the Solar System.
Orbit of Jupiter
Jupiter is the only planet with a barycenter with the Sun located outside the volume of the Sun, albeit only about 7% of the Sun’s radius. The average distance between Jupiter and the Sun is 778 million km (5.2 times the distance from Earth to the Sun, or 5.2 AU), and it completes an orbit in 11.86 Earth years.
Moons of Jupiter
As of July 2018, Jupiter has 79 natural satellites. Among these, 63 moons have a diameter of less than 10 kilometers and were only discovered since 1975. The four largest moons, known as the Galilean moons, are Io, Europa, Ganymede, and Callisto.
Exploration of Jupiter
Since 1973, several spacecraft have approached Jupiter, notably Pioneer 10, the first spacecraft to come close enough to the planet to send back photographs and data about the largest planet in the Solar System.
In 2000, the Cassini spacecraft, on its way to Saturn, flew by Jupiter and sent back some of the best-resolution images of the planet to date. On December 19, 2000, the spacecraft captured images of the moon Himalia, but the resolution was too low for scientists to discern details of its surface.
To date, only the Galileo spacecraft has orbited Jupiter, entering orbit around the planet on December 7, 1995. It conducted investigations for more than 7 years, making multiple flybys of the Galilean moons and the moon Amalthea.
NASA is currently planning a mission to Jupiter to study its polar regions and atmosphere in detail. The Juno spacecraft was launched in August 2011 and entered Jupiter’s polar orbit in late 2016. In the future, a planned mission has been approved to study the Jovian system led by the European Space Agency, known as the Jupiter Icy Moons Explorer (JUICE), scheduled for launch in 2022 and arrival at Jupiter around 2030, focusing on the four Galilean moons, particularly Europa.
