Solar System/Jupiter

Natural color photograph of Jupiter.

Jupiter is the fifth planet from the Sun. It is by far the largest planet, with a diameter of 142,984 kilometers (11.2 times that of Earth). Its mass is 317 times that of Earth. The volume of all the other planets combined is only 69% of Jupiter's volume; 1266 Earths would fit inside it. Jupiter is one of the four gas giants. If Jupiter had a solid surface and you stood on it, you would weigh 2.5 times what you weigh on Earth.

Physical characteristics

Jupiter is the giant planet of the Solar System, its diameter being eleven times greater than planet Earth's. Also, Jupiter's mass is over 300 times greater than Earth's. Jupiter rotates in less than ten hours, causing the middle of the planet to bulge out and the planet to flatten at its poles. This planet is a gas planet made up of hydrogen and helium, and what appears to be its surface is, in fact, the top of its atmosphere, which has swirls of other gases such as methane and ammonia.

Jupiter might be a giant planet, but it is not solid. Inside, it is made up mostly of liquid hydrogen. At the center lies a small core of rock and iron, which is believed to reach temperatures of at least 36,032 degrees Fahrenheit. Jupiter does not get much heat from the sun because it is so far away; this planet gives out its own heat. Heat rises from the center of Jupiter to the surface and passes into the atmosphere. The heat moves into belts of cooler gases which surround the planet.

Across Jupiter are dark bands, which change in darkness, size, and position from time to time. They are separated by lighter bands called zones. Like the wind patterns in Earth's atmosphere, the bands and zones on Jupiter are caused by heat. Also, Jupiter has a thin ring around it, like Saturn's but much smaller.

Rotation

Jupiter rotates prograde (in the same direction as it orbits) once every 9 hours 55.5 minutes, with its axis tilted just 3.13° from the perpendicular of its orbit.

Orbit

Jupiter orbits the Sun once every 11.86 Earth-years, at an average distance of 5.46 AU (Earth-Sun distances) and with an orbital eccentricity of .048.

Atmosphere

Clouds and winds

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  Blue clouds on Jupiter
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  Northern temperate belt

The Great Red Spot

Great Red Spot closeup.

The Great Red Spot is a swirling storm hanging in Jupiter's atmosphere lying across two bands in the southern hemisphere. It is about 25,000 miles across- over three times the diameter of the Earth- and rotates counter clockwise with a period of around six days. The color is most likely due to phosphine brought up from lower layers, which is broken down by sunlight to create red sulfur.

Jupiter's Great Red Spot is approximately five miles higher than the clouds. The Pioneer and Voyager space probes found that the Great Red Spot is very cold which means that its top is very high in the atmosphere. At the spot's center, gas spirals up, raising pressure in a dome shape. The Great Red Spot is the largest storm in the solar system. It whips violently around Jupiter and has raged in the planet's atmosphere for more than 300 years.

Polar Weather

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  North Pole weather in infrared.
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  Jupiter's south pole in enhanced color.

The magnetic field

Aurora above Jupiter

The rings of Jupiter

The rings are very thin and dark unlike Saturn's rings that are thick and made of ice. Jupiter's rings are made of rock and other hard materials.

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  Diagram of the rings of Jupiter.

Satellites

Jupiter has 79 moons, which 53 have been named, and 61 are less than 10 kilometers (6.2 mi) in diameter. Jupiter's sixteen largest moons divide into four groups. The four nearest Jupiter are tiny, next are the four large Galilean moons, much farther out are two clusters of four small, dark moons, and the farthest group of moons travels around Jupiter backwards compared to the other moons.

The four Galilean satellites

The Galilean moons are named after an Italian astronomer, Galileo Galilei, who first spotted them in 1610. Io and Europa were discovered on the 7th of January while Callisto and Ganymede were discovered on the 8th of January

Io

The inner two of the Galilean moons are Io and Europa, both of which are roughly the size of Earth's Moon. Io is a bright, red-orange world; it is covered with volcanoes. Clouds of sulfur and sulfur dioxide spew out of vents on Io's surface because the rock below the surface is hot and molten. Plumes rise up to 200 miles (320 km) high. Io is home to the most energetic volcano in the solar system, Loki. Io is heated inside by constant twisting and turning due to the gravity of Jupiter, Europa, and Ganymede. The closeness to its planet is the reason for all its activity. The pull of the planet's gravity raises tides inside the moon, which produce heat and cause eruptions.

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  True color photograph of Io.
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  Io contains a number of large Volcanos.
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  Photo of Io with volcanic eruption plume visible.

Europa

Europa is one of the two Galilean inner, large moons along with Io. Europa is covered by smooth ice. Jupiter's powerful gravity stirs Europa's icy crust and causes it to heat up; researchers believe there is liquid water below the moon's surface. This raises the question, "Could alien microbes have evolved in the waters of Europa?" Hydrothermal vents, like those on Earth's seafloor, may provide an energy source and create mineral-rich environments at the bottom of its ocean. Scientists are planning bold missions to this moon.

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  Photo of Europa
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  Closeup
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  Surface closeup
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  Potential internal models.

Ganymede

Ganymede is the largest planetary satellite in the solar system, and in fact its diameter is 8% larger than the planet Mercury's. It has a small magnetic field and a thin atmosphere.

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  Ganymede
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  Diagram of internal structure.

Callisto

Callisto is Jupiter's second largest moon and the third largest in the solar system. Its diameter is 98% of that of Mercury. It has one of the oldest and most heavily cratered surface in the solar system.

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  Callisto
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  Valhalla impact structure.
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  Diagram of internal structure.