What It Is
Jupiter is the largest planet in the solar system, a fast-spinning gas giant made mostly of hydrogen and helium. In small-telescope images, its bright disk is often seen with the four Galilean moons, which line up near the planet as they orbit.
History
Jupiter has been known since antiquity because it is bright enough to see without a telescope. In January 1610, Galileo Galilei observed points of light near Jupiter and soon recognized them as moons orbiting the planet, a discovery that became strong evidence that Earth was not the center of all motion in the heavens.
Science Notes
- Jupiter is 11 times wider than Earth and more massive than all the other planets combined.
- A Jovian day lasts only about 9.9 hours, the shortest day of any planet in the solar system.
- The Great Red Spot is a long-lived storm larger than Earth in Jupiter's atmosphere.
- Jupiter has 95 officially recognized moons; the four largest are Io, Europa, Ganymede, and Callisto.
- Europa may have a liquid-water ocean beneath its icy crust, making it one of the solar system's most interesting places to study habitability.
- NASA's Juno spacecraft entered orbit around Jupiter on July 4, 2016, and has measured the planet's atmosphere, magnetic field, and interior.
- planetClass
- Gas giant
- diameter
- 86,881 miles / 139,822 kilometers at the equator
- radius
- 43,440.7 miles / 69,911 kilometers
- averageDistanceFromSun
- 484 million miles / 778 million kilometers / 5.2 AU
- dayLength
- 9.9 Earth hours
- yearLength
- About 12 Earth years / 4,333 Earth days
- recognizedMoons
- 95 officially recognized moons
- notableMoons
- Io, Europa, Ganymede, and Callisto
