Jupiter

True Color Mosaic of Jupiter Credit: NASA Solar System

Jupiter is the largest planet in the solar system. Fittingly, it was named after the king of the gods in Roman mythology. In a similar manner, the ancient Greeks named the planet after Zeus, the king of the Greek pantheon.

Equatorial Diameter: 142,984 km

Polar Diameter: 133,709 km

Moons: 67 (Io, Europa, Ganymede & Callisto)

Rings: 4

Orbit Distance: 778,340,821 km (5.20 AU)

Orbit Period: 4,333 days (11.9 years)

Effective Temperature: -148 °C

First Record: 7th or 8th century BC

Recorded By: Babylonian Astronomers

Jupiter helped revolutionize the way we saw the universe and ourselves in 1610, when Galileo discovered Jupiter's four large moons — Io, Europa, Ganymede and Callisto, now known as the Galilean moons. This was the first time celestial bodies were seen circling an object other than Earth, major support of the Copernican view that Earth was not the center of the universe.

Jupiter is the most massive planet in our solar system, more than twice as massive as all the other planets combined, and had it been about 80 times more massive, it would have actually become a star instead of a planet. Its atmosphere resembles that of the sun, made up mostly of hydrogen and helium, and with four large moons and many smaller moons in orbit around it, Jupiter by itself forms a kind of miniature solar system. All told, the immense volume of Jupiter could hold more than 1,300 Earths.

The most extraordinary feature on Jupiter is undoubtedly the Great Red Spot, a giant hurricane-like storm seen for more than 300 years. At its widest, the Great Red Spot is three times the diameter of the Earth, and its edge spins counterclockwise around its center at a speed of about 225 mph (360 kph). The color of the storm, which usually varies from brick red to slightly brown, may come from small amounts of sulfur and phosphorus in the ammonia crystals in Jupiter's clouds. The spot grows and shrinksover time, and every now and again, seems to fade entirely.

Jupiter spins faster than any other planet, taking a little under 10 hours to complete a turn on its axis, compared with 24 hours for Earth. This rapid spin makes Jupiter bulge at the equator and flatten at the poles, making the planet about 7 percent wider at the equator than at the poles.

Significant Dates:

• 1610: Galileo Galilei makes the first detailed observations of Jupiter.
• 1973: Pioneer 10 becomes the first spacecraft to cross the asteroid belt and fly past Jupiter.
• 1979: Voyager 1 and 2 discover Jupiter's faint rings, several new moons and volcanic activity on Io's surface.
• 1992: Ulysses swung by Jupiter on Feb. 8, 1992. The giant planet's gravity bent the spacecraft's flight path southward and away from the ecliptic plane, putting the probe into a final orbit that would take it over the sun's south and north poles.
• 1994: Astronomers observe as pieces of comet Shoemaker-Levy 9 collide with Jupiter's southern hemisphere.
• 1995-2003: The Galileo spacecraft drops a probe into Jupiter's atmosphere and conducts extended observations of Jupiter and its moons and rings.
• 2000: Cassini makes its closest approach to Jupiter at a distance of approximately 6.2 million miles (10 million kilometers), taking a highly detailed true color mosaic photo of the gas giant.
• 2007: Images taken by NASA's New Horizons spacecraft, on the way to Pluto, show new perspectives on Jupiter's atmospheric storms, the rings, volcanic Io, and icy Europa.
• 2009: On 20 July, almost exactly 15 years after fragments of comet Shoemaker-Levy slammed into Jupiter, a comet or asteroid crashes into the giant planet's southern hemisphere.
• 2011: Juno launches to examine Jupiter's chemistry, atmosphere, interior structure and magnetosphere.
• 2016: NASA's Juno spacecraft arrives at Jupiter, conducting an in-depth investigation of the planet's atmosphere, deep structure and magnetosphere for clues to its origin and evolution.

Credit: Karl Tate/Space.com

Reference: Karl Tate/spacedotcom/Nasa Solar System