Facts about the Planet Jupiter

Facts about the Planet Jupiter

The fifth and the largest of the planets in our Solar System, Jupiter has often been referred to as the King of the Planets due to its size and sheer impressiveness. Just like any king, it even has one of the highest retinue of other bodies in orbit.


Jupiter is 11 times wider than the Earth, with an equatorial diameter of 88,846 miles (or 142,984 km) and the brightest body in the Solar System after the Sun, the Moon and Venus (sometimes after Mars). It is 483,682,792 miles from the sun and was first recorded by Babylonian astronomers around 3300 BCE and then by the ancient Greeks and Chinese, sharing a prominent role in mythology and legends.

A giant gas planet, Jupiter is largely made up of 75% hydrogen, 25% helium and then traces of other gases. Scientists cannot confirm at this moment, but they believe the core of Jupiter is made of rock 10 times larger than the Earth, and then covered by hydrogen that has become compressed by the incredible pressure and then turned into liquid metallic hydrogen. After this, there is a layer of liquid hydrogen and helium before a layer of hydrogen and helium gas close to the surface layer. On the very top, scientists believe that the atmosphere is made up of cloud layers compiled of ammonia ice crystals, water and/or ice, and maybe ammonium hydrosulphide.

When the Galileo atmospheric probe came into contact with Jupiter, NASA hoped that it would be able to trace some water in one of the cloud layers but, unfortunately, it didn’t. Scientists have believed that the Galileo just went into a dry region.

Orbit and Rotation:

At 9 hours and 55 Earth minutes, Jupiter has the fastest rotation speed in the Solar System. Because of this, the planet has a ‘flatten out’ look to it, with a slight bulge on its side. One Jupiter year takes 11.9 Earth years.

Because of its positioning in the middle of Solar System, Jupiter’s large gravitational field affects the movement of smaller bodies including comets and asteroids. It actually keeps some bodies in their own orbit and then flings others away when they come too close to the planet.

A Failed Star:

One fact that makes Jupiter is that it is often called a failed star. At 1% smaller than the Sun, if it had been 12 times larger it would have been classed as a brown dwarf (a star that releases a small amount of heat); if it was 80 times larger, it would have been a true star, albeit a small one.

Another interesting fact is that it reflects the same amount of heat as it receives from the Sun. When it absorbs the Sun’s heat, it slowly releases it as it contracts and this has now led to Jupiter being half the diameter it was when it was first formed.


On looking at Jupiter, we see that the planet is made up of different and distinctive bands or stripes. The darker coloured cloud patterns are called belts, whilst the lighter ones are called zones. The hemispheres are divided into three belts and three zones with an extra one which overlaps the equator. Additionally, there are two Polar Regions as well as several other zones and belts which fluctuate.

These different colours are caused by reflecting the different gases composing the clouds; these clouds are made up from three layers as well. Ammonia makes up the first layer; the second through ammonium hydrosulphide; and the third is composed of water clouds but these are not generally visible underneath the first and second layers.


Just like Earth, Jupiter has circulation patterns giving it an intricate climate structure. The air gets warmer from the equator and gets pushed towards the poles, and the cold air gets pushed away from the poles. Along with the powerful Coriolis Effect (created from the rapid rotation of the planet), this leads to the formation of strong currents in the atmosphere.


Within the Solar System, Jupiter has the largest amount of moons circling the planet; there are 63 moons known at present. When the telescope was invented some 400 years ago, a number of moons were discovered but it wasn’t until the formation of space programs and spacecrafts that scientists found others. It is believed that some were created at the same time Jupiter came into being, whilst others were captured by the planet’s strong gravity force.

The first four moons were discovered by Galileo Galilei in January of 1610 using the telescope. Looking at the planet, he found four dots following Jupiter and after watching them for a few nights, he realised that they were actually following it.

This discovery led to some serious debates as it showed that the Earth was not the centre of the world as it was believed at the time. His discovery led to this type of belief and one in favour of evidence and reason. These four moons were named Jupiter I, II, III and IV. In the mid 19th century, their names were changed to Io, Europa, Ganymede and Callisto from Greek mythology, proposed originally by a contemporary of Galileo, Simon Marius, and now known collectively as the Galilean moons.

Io is the innermost moon a little over 2,236 miles (3,600 km) in diameter. Scientists are interested in Io due to her being one of the biggest moons in the Solar System, the densest and have the most volcanic activity. When the Voyager 1 probe came near Io, it witness nine volcanic eruptions.

The volcanoes do not erupt lava as they do on Earth; instead, they erupt sulphur compounds which some get caught in Io’s orbit which creates a ring in the shape of a donut, called a torus, which extends to Jupiter itself. The volcanic activity on Io is the reason for the geologically young appearance of the moon, with hardly any craters visible.

The volcanoes are caused by the energy created by the gravitational tug of war between Io and Jupiter as well as the other moons. They all pull Io in different directions, leading to Io to be stretched, causing internal heat and the volcanoes to erupt.


Jupiter has a system of rings, just like Saturn, although they are no way as spectacular as the other planet. Jupiter’s rings are made up of dust particles instead of ice. Scientists did not believe that Jupiter had a system of rings unto Voyager 1 past it in March 1979 when three rings were discovered. There is an inner halo torus, a vivid main ring and a three part transparent ring. Each ring has their own moons and it is believed that these rings are made up from the material flung from the surface of these moons when meteorites had struck them.

Visits to Jupiter:

Eight spacecraft has made it out as far as Jupiter but only one has spent any significant time at Jupiter to gather information. The first crafts to reach Jupiter was Pioneer 10 and 11 in December 1973 and December 1974, shortly followed by Voyager 1 and 2 a few years later.

NASA has implemented a new program to reach Jupiter shortly; it is hoped that fresh information will help us understand the wonders of this incredible planet and further our knowledge of science and the universe.