Jupiter

Jupiter is a giant planet with a mass one-thousandth that of its parent star Sol, but two and a half times that of all the other planets in the Solar System combined. It is only fitting that it is named after the god Jupiter, who presides over the Roman pantheon as chief deity. In Roman mythology Jupiter came to power after he defeated and banished his father Saturn.

## Surface Conditions

### Atmosphere

* 89.8% H2
* 10.2% He
* 0.3% CH4

## Additional Information

### Moons

4 main moons:* Io
* Europa
* Ganymede
* Callisto

63 dwarf moons:

* Amalthea

### Position in Star System

5th (6th in Space Engine, as dwarf planets are counted too)

## Overview

Jupiter is the fifth planet from the sun and the largest of the Solar System, as well as the planet with the most moons. Viewed from Earth, Jupiter can reach an apparent magnitude of nearly -3m, making it the third brightest object in the night sky after the Moon and Venus. It has been considered a powerful deity for thousands of years in many mythologies due to its brightness, and modern-day explorations are proving that these ideas were more accurate than otherwise might have been assumed.

## Composition and Atmosphere

As a gas giant, Jupiter has nothing that could be considered a 'surface' - its atmosphere simply transitions smoothly from gas to liquid to solid as it gets deeper. It's composed mostly of hydrogen and helium, with only small amounts of other elements. Numerous storms exist on its surface at any one time, notably the Great Red Spot, an anticyclonic storm the size of the Earth which has been active for at least three hundred years.

* Artistic depicition of Jupiter's clouds. Painting by Adolf Schaller
* Artistic depicition of Jupiter's clouds. "Shadow of Io" by sirgerg
* Artistic depicition of Jupiter's clouds. "Jupiter" by justV23
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## Moons

Jupiter's first four moons were discovered by Galileo Galilei in 1610, and today are known as the 'Galilean' moons in his honor - of its total of 67 moons, the Galilean moons are the largest and most massive, making up 99.9997% of the total mass in orbit around Jupiter, and all except Europa are larger than the Earth's moon. The remaining 63 moons are very small by comparison, barely more than asteroids. The innermost Galilean moon, Io, is currently the only location in the solar system other than the Earth to exhibit active volcanism. Second is Europa, the smallest of the Galilean moons, covered in a shell of thick ice and theorized to possess an ocean of liquid water underneath this ice sheet. Third and Fourth are Ganymede and Callisto, respectively. Both are composed mostly of water ice, and may also hold subsurface oceans like Europa.

## Rings

Like all gas giants in the solar system, Jupiter has rings. However, they are very tenuous and dark, being mostly composed of material ejected from Io's volcanoes, and the debris from meteoroid impacts on various moons.

## Orbit

Jupiter occupies a typical circular orbit, with a semi-major axis of 5.2 AU, an inclination of 1.3°, and a low eccentricity value of 0.04.

## Exploration

Jupiter wasn't explored directly until 1973, when Pioneer 10 conducted a flyby, returning the first images from beyond the orbit of Mars. Pioneer 10 was followed a few months later by Pioneer 11 (which later went on to explore Saturn). In 1979, the twin Voyager probes arrived. In 1992, the Ulysses probe used Jupiter's strong gravity to alter its trajectory, allowing it to pass over the poles of the Sun a few years later. In 1995, the Galileo spacecraft became the first to orbit Jupiter, and operated continuously until 2003, when it was intentionally crashed into the atmosphere to avoid any chance of the inactive spacecraft impacting (and contaminating) Europa. The Cassini spacecraft, en-route to Saturn, conducted a flyby in 2000, returning the highest resolution imagery of Jupiter to date. Finally, in 2007, the New Horizons spacecraft en-route to Pluto conducted a flyby of Jupiter, testing its instruments to help prepare for the Pluto encounter in 2015.

1. ↑ This article has been adapted from the Space Engine ingame wiki

## Images

Jupiter's *Great Red Spot*Jupiter's North Polar RegionJupiter's crescentOverview of Equatorial and Temperate BeltsJupiter's North Polar RegionClose-up of the South Temperate BeltNorth Equatorial Belt and South Equatorial BeltJupiter's North Equatorial BeltJupiter seen from its moon IoJupiter seen from its moon GanymedeJupiter seen from its moon EuropaJupiter seen from its moon CallistoJupiter looming in the skyJupiter seen from its moon AdrasteaPart of Jupiter's northern hemisphere