Rings of Jupiter Rings of Jupiter The planet Jupiter has a system of rings known as the rings of Jupiter or the Jovian ring system. It was the third ring system to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed in 1979 by the "Voyager 1" space probe and thoroughly investigated in the 1990s by the "Galileo" orbiter. It has also been observed by the Hubble Space Telescope and from Earth for several years. Ground-based observations of the rings require the largest available telescopes. The Jovian ring system is faint and consists mainly of dust.
IAU definition of planet IAU definition of planet The International Astronomical Union (IAU) defined in August 2006 that, in the Solar System, a planet is a celestial body which: Among other things, this definition caused Pluto to no longer be a planet, a change from how it had been widely considered until that point. A non-satellite body fulfilling only the first two of these criteria (such as Pluto) is classified as a "dwarf planet". According to the IAU, "planets and dwarf planets are two distinct classes of objects". A non-satellite body fulfilling only the first criterion is termed a "small Solar System body" (SSSB).