Astrobiology Glossary J – Space

Term Definition
Jets Narrow, high-energy streams of gas and other particles generally ejected in two opposite directions from some central source. Jets appear to originate in the vicinity of an extremely dense object, such as a black hole, pulsar, or protostar, with a surrounding accretion disk. These jets are thought to be perpendicular to the plane of the accretion disk.
Jovian Atmosphere The atmosphere surrounding the giant, massive planet Jupiter. The Jovian atmosphere is composed primarily of hydrogen (90 percent) and helium (10 percent). Other minor ingredients include water, hydrogen sulfide, methane, and ammonia.
Jovian Planets The planets Jupiter, Saturn, Uranus, and Neptune. They are called Jovian planets because of similarities in their composition and location. This group is also known as the ‘giant planets,’ the ‘gas planets’ and, when grouped with the planet Pluto, the ‘outer planets.’
Jovian Winds The hurricane-force, high-velocity motion of gas molecules in Jupiter’s atmosphere. The wind speed increases as one travels deeper into Jupiter’s atmosphere. The various patterns of atmospheric winds are easily identified in Jupiter’s upper cloud layer.
Jupiter The fifth planet from the Sun and the largest planet in our solar system, twice as massive as all the other planets combined. Jupiter is a gaseous planet with a very faint ring system. Four large moons and numerous smaller moons orbit the planet. Jupiter is more than five times the Earth’s distance from the Sun. It completes an orbit around the Sun in about 12 Earth years.