The Jovian planets are four planets in the outer atmosphere also called ‘Gas Giants’, Jupiter, Saturn, Neptune and Uranus. Made up of a mixture of gases, primarily hydrogen and helium, they are unique in their chemical compositions with many differences to rock-based planets, the terrestrial planets Mercury, Venus, Earth and Mars.
They are larger than other planets (Jupiter is 318 times the size of Earth), but they also have lower densities due to their gaseous state. Deep within this thick atmosphere is believed to be a dense solid core; each layer of gas condenses the mass below it creating this core, possibly a heavy liquid metal which mimics a rock formation. These are ten times the mass of the liquid core inside the Earth.
The magnetic field of the gas giants exceeds that of the one around our Earth. Jupiter’s is the strongest, this combined with its moon Io’s volcanic gases creates a large torus (plasma cloud) around the planet.
The Jovian planets have wind and cloud systems within their layers, each with different colour clouds due to the compounds making up the planet. They all experience strong winds and storms; Jupiter’s red spot has been raging for around three centuries.
Many moons orbit each of the Jovian’s; Jupiter has sixty-three moons while Saturn has fifty-two named moons, Titan being the largest, to date; sixty-one moons have been identified around this planet.
Due to their distances from the sun, between five to thirty times the Earth’s distance to the sun, they receive almost no heat. However Jupiter, Saturn and Neptune emit more energy then they obtain, this is due to the chemical reactions and a slow contraction of the interior taking place within the planet. Uranus is the exception releasing little or no heat.
Neptune and Uranus also have the nickname ‘Ice Giants’ as they also contain ammonia and methane, creating ices in the atmospheres. The amount of ammonia in Neptune’s gases gives it the bright blue colour of the sea. They are denser than Saturn and Jupiter.
Saturn and Neptune are circled by rings, gases and rocks formed in a disk surrounding the planets. Saturn’s are clearly visible by telescope but Neptune’s could not be confirmed until the Voyager probe detected them in 1989.
Jovian planets spin faster than terrestrial planets making their days shorter and not quite spherical but neither are they flattened at the poles like terrestrial planets; with their elliptical orbits and distance from the sun, their years are longer.
Several other gas giants have been discovered in outer space but due to the dense gaseous surface their secrets remain deeply hidden.