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Jupiter (planet)

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Orbital characteristics
Mean radius7.7833×108 km
Revolution period11y 315d 1.1h
Synodic period398.9 days
Avg. Orbital Speed13.1 km/s
Number of satellites61
Physical characteristics
Equatorial diameter142,984 km
Surface area6.41×1010[?] km2
Mass1.899×1027 kg
Mean density1.33 g/cm3
Surface gravity22.88 m/s2
Rotation period9h 55.5m
Axial tilt3.12°
Escape Speed60.2 km/s
Surface temp.
110 K 152 K N/A K
Atmospheric characteristics
Atmospheric pressure70 kPa
Water vapor0.1%
Hydrogen sulfide<0.0001%

Jupiter is the fifth planet from the Sun and by far the largest in Earth's solar system. The gas giant is more than twice as massive as all the other planets combined (318 times more massive than Earth, with a diameter 11 times that of Earth). Some have described the solar system as consisting of Sol, Jupiter and assorted debris.

Table of contents

Physical characteristics

Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus; at some times Mars is also brighter). It has been known since prehistoric times. Galileo Galilei's discovery, in 1610, of Jupiter's four large moons Io, Europa, Ganymede and Callisto (now known as the Galilean moons) was the first discovery of a celestial motion not apparently centered on the Earth. It was a major point in favor of Copernicus's heliocentric theory of the motions of the planets; Galileo's outspoken support of the Copernican theory got him in trouble with the Inquisition.

Jupiter is composed of about 90% hydrogen and 10% helium (by numbers of atoms, 75/25% by mass) with traces of methane, water, ammonia, and "rock". This is very close to the composition of the primordial solar nebula from which the entire solar system was formed. Saturn has a similar composition, but Uranus and Neptune have much less hydrogen and helium.

Jupiter has a faint planetary ring system composed of smoke-like dust particles knocked off of its moons by meteor impacts. The main ring is made of dust from the satellites Adrastea and Metis. Two wide gossamer rings encircle the main ring, originating from the Thebe and Amalthea. There is also an extremely tenuous and distant outer ring that circles Jupiter backwards. Its origin is uncertain, but this outer ring might be made of captured interplanetary dust.

One of Jupiter's most distinctive features is the Great Red Spot, a large hurricane colored by reddish methane-rich gases welling up from lower in the Jovian atmosphere. The Great Red Spot is remarkably stable, having first been spotted by Galileo over 300 years ago.

Jupiter has a very large and powerful magnetosphere. In fact, if you could see Jupiter's magnetic field from Earth, it would appear five times as large as the full moon in the sky despite being so much farther away. This magnetic field collects a large flux of particle radiation in Jupiter's radiation belts, as well as producing a dramatic gas torus and flux tube associated with Io.

Voyager 1 took this photo of the planet Jupiter on January 24, while still more than 25 million miles (40 million kilometers) away. As the spacecraft draws closer to the planet (about 1 million kilometers a day) more details are emerging in the turbulent clouds. The Great Red Spot shows prominently below center, surrounded by what scientists call a remarkably complex region of the giant planet's atmosphere. An elongated yellow cloud within the Great Red Spot is swirling around the spot's interior boundary in a counterclockwise direction with a period of a little less than six days, confirming the whirlpool-like circulation that astronomers have suspected from ground-based photographs. Ganymede, Jupiter's largest satellite, can be seen to the lower left of the planet. Ganymede is a planet-sized body larger than Mercury. This color photo was assembled at Jet Propulsion Laboratory's Image Processing Lab from three black and white images taken through filters. (larger image)

The exploration of Jupiter

A number of probes have visited Jupiter, all of them American in origin. Pioneer 10 flew past Jupiter in December of 1973, followed by Pioneer 11 exactly one year later. Voyager 1 flew by in 1977 and Voyager 2 in 1979. The Galileo probe went into orbit around Jupiter in 1995, dropping a smaller subprobe into Jupiter's atmosphere and conducting multiple flybys of all of the Galilean moons. The Galileo probe also witnessed the impact of Comet Shoemaker-Levy 9 into Jupiter as it approached the planet in 1994, giving a unique vantage point for this spectacular event.

Jupiter's Moons

Jupiter's 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). From the top, they are Io, Europa, Ganymede and Callisto.

The orbits of Io, Europa and Ganymede form a pattern known as a Laplace resonance; for every four orbits that Io makes around Jupiter, Europa makes exactly two orbits and Ganymede makes exactly one. This resonance causes the gravitational effects of the three moons to distort their orbits into elliptical shapes, since each moon receives an extra tug from its neighbors at the same point in every orbit it makes. The tidal force from Jupiter, on the other hand, works to circularize their orbits. This constant tug of war causes regular flexing of the three moons' shapes, Jupiter's gravity stretching the moons more strongly during the portion of their orbits that are closest to it and allowing them to spring back to more spherical shapes when they're farther away. This flexing causes tidal heating of the three moons' cores. This is seen most dramatically in Io's extraordinary volcanic activity, and to a somewhat less dramatic extent in the geologically young surface of Europa indicating recent resurfacing.

Jupiter's moons fall into four major groups:

  1. The inner group were all discovered during the Voyager program except for Amalthea, all have diameters of less than 200 km and orbit at radii less than 200,000 km, and have orbital inclinations of less than half a degree.
  2. The Galilean moons were all discovered by Galileo Galilei, orbit between 400,000 and 2,000,000 km, and include the largest moons in the solar system.
  3. The third group were all discovered in the 20th century but before Voyager, have diameters less than 200 km, and orbit between 11,000,000 and 12,000,000 km with an orbital inclination between 26° and 29°.
  4. The outer moons were also discovered in the 20th century before Voyager, but have diameters under 50 km and orbit between 21,000,000 and 24,000,000 km. They are particularly notable for having retrograde orbits with inclinations between 147° and 163°.

It is thought that the three groups of smaller moons may each have a common origin, perhaps as a larger moon or captured body that broke up into the existing moons of each group.

In addition to the 16 moons listed below there are a further 42 tiny moons in long, eccentric, retrograde orbits around Jupiter, most no larger than a kilometer or two in diameter. All of these moons are thought to be captured asteroidal or perhaps cometary bodies, possibly fragmented into several pieces, but very little is actually known about them. The total number of known moons of Jupiter is therefore 52, currently the most of any planet in the solar system. Many additional tiny moons may exist that have not yet been discovered.

On April 4, 2003, the official moon count for Jupiter jumped to 58. The latest discoveries were made by a team led by Scott Sheppard[?] and David Jewitt[?] at the University of Hawaii[?], along with Jan Kleyna[?] of Cambridge University. The discoveries were made using the world's two largest digital cameras at the Subaru and Canada-France-Hawaii telescopes[?] atop Mauna Kea[?] in Hawaii. All six newfound satellites are estimated to be about 2 kilometers wide. The same team earlier this year found the smallest known moons, a pair of 1-kilometer satellites orbiting the giant planet. The same team has later announced a few more moons and presently the official moon count for Jupiter is 61

Reference: http://www.ifa.hawaii.edu/~sheppard/satellites/jup2003

Jupiter's natural satellites
Group Name Diameter (km) Mass (kg) Mean orbital
radius (km)
Orbital period
1 Metis 40 (40 x 60) 9.56×1016 127,600 7.08 hours
Adrastea 20 (23 x 20 x 15) 1.91×1016 134,000 7.11 hours
Amalthea 189 (270 x 166 x 150) 7.17×1018 181,300 11.92 hours
Thebe 100 (100 x 90) 7.77×1017 222,000 16.23 hours
2 Io 3632 8.92×1022 421,600 1.76 days
Europa 3138 4.8×1022 670,900 3.55 days
Ganymede 5262 1.49×1023 1,070,000 7.16 days
Callisto 4820 1.08×1023 1,883,000 16.69 days
3 Leda 16 5.68×1015 11,100,000 238.7 days
Himalia 186 9.56×1018 11,470,000 250.6 days
Lysithea 36 7.77×1016 11,710,000 259.2 days
Elara 76 7.77×1017 11,743,000 259.7 days
4 Ananke 30 3.82×1016 20,700,000 617 days
Carme 40 9.56×1016 22,350,000 692 days
Pasiphae 50 1.91×1017 23,300,000 735 days
Sinope 36 7.77×1016 23,700,000 758 days

All Jovian moons are tidally locked with Jupiter, and therefore have the same rotational period as their orbital period.

Cometary impact

During the period July 16 to July 22, 1994, over twenty fragments of the comet Shoemaker-Levy 9 collided with Jupiter's southern hemisphere, providing the first direct observation of the collision of two solar system objects. It is thought that due to Jupiter's large mass and location near the inner solar system it receives the most frequent comet impacts of the solar system's planets.

Miscellaneous Information

Jupiter is also home to Jupiter Station, a fictional space station in the Star Trek universe.

Solar system:
Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets

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