Jupiter is the fifth
planet from the
Sun and the
largest planet within the
system. It is two and a half times as massive as all of the other planets
combined, and is classified as a
planet. Jupiter shares the gas giant classification with three other planets in
the Solar System, namely
Together, these four planets are sometimes referred to as the
Jovian planets (Jovian being the adjectival form of Jupiter,
derived from the Latin
When viewed from Earth, Jupiter can reach an
apparent magnitude of -2.8, making it the third brightest object in the
night sky. The planet was known to
of ancient times. The Romans named it after
Jupiter, the principal
Roman mythology (the name being a reduction of 'Deus Pater', 'God father'
during the era of
Planet Jupiter: "Bringer of Jollity"
The planet Jupiter is primarily composed of
with a smaller portion of
helium and a
rocky core. Due to its rapid rotation the planet possesses a slight but
noticeable bulge around the equator, giving it an
appearance. The outer atmosphere is visibly segregated into several bands at
different latitudes, resulting in turbulence and storms along their interacting
boundaries. A prominent result is the
Great Red Spot, a giant storm that has been existent since at least the
seventeenth century. Surrounding the planet is a faint planetary ring system and
magnetosphere. There are also at least 63 moons, including the four large
moons that were first discovered by
Galileo Galilei in 1610.
Jupiter has been explored on several occasions by robotic spacecraft; most
notably during the early
Voyager fly-by missions, and later by the
Galileo orbiter. Future targets for exploration include the possible
ice-covered liquid ocean on the Jovian moon
Jupiter is usually the fourth brightest object in the night sky (after the
Sun, the Moon and
however at times Mars
appears brighter than Jupiter.
Jupiter is 2.5 times more
massive than all
the other planets combined; so massive that its
barycenter with the Sun actually lies above the Sun's surface (1.068
radii from the Sun's centre). Although this planet dwarfs the Earth (with a
diameter 11 times as great) it is considerably less dense. A volume equal to
1,300 Earths only contains 318 times as much mass.
Along with the Sun, the
influence of Jupiter has helped shape the Solar System. The orbits of most of
the system's planets lie closer to Jupiter's
orbital plane than the Sun's
equatorial plane (Mercury
is the only planet which is closer to the Sun's equator in orbital tilt), the
short-period comets belong to Jupiter's family (a result due to both
Jupiter's mass and its relative speed), the
Kirkwood gaps in the
asteroid belt are mostly due to Jupiter, and the planet may have been
responsible for the
Late Heavy Bombardment of the inner solar system's history.
Jupiter has been called the solar system's vacuum cleaner,
due to its immense
Extra solar planets have been discovered with much greater masses. There is
no clear-cut definition of what distinguishes a large planet such as Jupiter
brown dwarf star, although the latter possesses rather specific
spectral lines. Currently, if an object of solar
metallicity is 13 Jupiter masses or above, large enough to burn
it is considered a brown dwarf; below that mass (and orbiting a star or stellar
remnant), it is a planet.
Jupiter is thought to have about as large a diameter as a planet of its
composition can; adding extra mass would cause the planet to shrink due to
increased gravitational compression. The process of further shrinkage with
increasing mass would continue until
stellar ignition is achieved.
This has led some astronomers to term it a "failed star". Although Jupiter would
need to be about seventy-five times as massive to become a
star, the smallest
is only about 30% larger in radius than Jupiter.
In spite of this, Jupiter still radiates more heat than it receives from the
Sun. This additional heat radiation is generated by the
Kelvin-Helmholtz mechanism through
contraction. This process results in the planet shrinking by about 3 cm each
When they were younger and hotter, Jupiter and the other gas giant planets were
much larger than they are today. However, because of its lower mass and weaker
Saturn would expand more rapidly than Jupiter with increasing heat;
therefore, Saturn must have formerly been even larger than Jupiter.
rotation is the solar system's fastest, completing a rotation on its
axis in slightly less than ten hours; this creates an
equatorial bulge easily seen through an Earth-based amateur
The planet is also perpetually covered with a layer of clouds, composed of
crystals and possibly ammonium hydrosulphide. Its best known feature is the
Great Red Spot, a
storm larger than Earth which was likely first observed by
Giovanni Domenico Cassini and
Hooke four centuries ago. Indeed, mathematical models suggest that the storm
is stable and may be a permanent feature of the planet.
In 2000, three small spots merged to form a larger spot named
which later acquired a red hue very similar to that of the Great Red Spot.
5.455 167 59 AU
4.951 558 43 AU
5.203 363 01
||0.048 392 66
(6.09° to Sun's
Longitude of ascending node:
Argument of perihelion:
(5.6045 Earth diameters)
(5.2585 Earth diameters)
|Sidereal rotation period:
||0.413 538 021 d
(9 h 55 min 29.685 s)
|Rotation velocity at equator:
||12.6 km/s = 45,300 km/h
(at the equator)
Right ascension of North pole:
||268.05° (17 h 52 min 12 s)
0.1% Water vapor
The planet Jupiter has been known since ancient times and is visible to the
naked eye in the night sky. The
named the planet after the
Jupiter (also called Jove). The
astronomical symbol for the planet is a stylized representation of the god's
lightning bolt. (♃ is found at
refer to the planet as the wood star, 木星,
based on the Chinese
Five Elements. In
Hindu astrologers refer to Jupiter as
or "Guru" which
means the "Big One". In
is referred to as
Guruvaar (day of Jupiter). In the
English language Thursday is rendered as Thor's day, with
identified with the Roman god Jupiter.
Galileo Galilei discovered the four largest
moons of Jupiter,
Callisto (now known as the
Galilean moons) using a telescope, the first observation of moons other than
Earth's. This was also the first discovery of a
celestial motion not apparently centered on the Earth. It was a major point
in favor of
heliocentric theory of the motions of the planets; Galileo's outspoken
support of the Copernican theory placed him under the threat of the
Barnard observed a fifth satellite of Jupiter with the 36-inch refractor at
Lick Observatory in California. The discovery, a testament to his
extraordinary eyesight, made him quickly famous. The moon was later named
Jupiter's upper atmosphere is composed of about 93%
and 7% helium
by number of atoms,
or approximately 75% hydrogen and 24% helium by mass, with the remaining 1% of
the mass accounted for by other substances. The interior contains denser
materials such that the distribution is roughly 71% hydrogen, 24% helium and 5%
other elements, by mass. The atmosphere contains trace amounts of
ammonia, and "rock". There are also traces of
The outermost layer of the atmosphere contains
Through IR and UV measurements
benzene (at a
relative mixing ratio of 2x10-9 to hydrogen) and other
hydrocarbons have also been found.
This atmospheric composition for hydrogen and helium is very close to the
composition of the
nebula. Galileo probe results show that neon in Jupiter's upper atmosphere
is unexpectedly only about a tenth as abundant as in the sun (20 parts per
million by mass, vs. 200 parts per million for the Sun)
. This depletion may be due to the fact that the ice which carried
heavier elements into Jupiter during formation was still too warm to hold all of
its nebular neon (this requires temperatures below 17 Kelvins). Abundances of
heavier inert gases in Jupiter's atmosphere are about 2 to 3 times solar
On the basic of spectroscopy,
thought to have a quite similar composition to Jupiter, but
relatively much less hydrogen and helium.
However, very good abundance numbers for heavier
elements are lacking for the other outer planets, due to lack of data from
atmospheric entry probes from these.
Shape and structure
Jupiter is an
oblate spheroid, meaning that the
equator is longer than the diameter measured between its
poles. On Jupiter, the equatorial diameter is 9275 km longer than the
diameter measured through the poles. This is caused by Jupiter's rapid
which causes the equator to bulge outward.
There is still some uncertainty regarding the interior structure of Jupiter.
One model shows a homogeneous model with no solid surface; the density may
simply increase gradually toward the core. Alternatively Jupiter may possess a
core with a mass of up to twelve times the Earth's total mass.
The core region is surrounded by dense
metallic hydrogen, with further layers of
liquid hydrogen and
gaseous hydrogen. There may be no clear boundary or surface between these
different phases of hydrogen; the conditions blend smoothly from gas to liquid
as one descends.
Because Jupiter is not a solid body, its upper atmosphere undergoes
differential rotation, an effect first noticed by
Giovanni Cassini (1690).
The rotation of Jupiter's
atmosphere is ~5 minutes longer than that of the
atmosphere; three "systems" are used as frames of reference, particularly when
graphing the motion of atmospheric features. System I applies from the latitudes
10º N to 10º S; its period is the planet's shortest, at 9h 50m 30.0s. System II
applies at all latitudes north and south of these; its period is 9h 55m 40.6s.
System III was first defined by
radio astronomers, and corresponds to the rotation of the planet's
magnetosphere; its period is Jupiter's "official" rotation.
Jupiter is wrapped by bands of clouds of different
known as tropical regions. These are sub-divided into lighter-hued zones
and darker belts. The interactions of these conflicting
circulation patterns cause storms and
of 600 km/h are not uncommon.
The outer atmosphere of Jupiter consists of two decks of clouds; a thick,
lower deck and a thin, clearer region. The coloration of the bands is caused by
the altitude at which clouds become visible. The darker coloration of the belts
is likely caused by upwellings of colorful compounds that mix with the warmer,
lower deck of clouds. The zones are formed when rising convection cells form
crystallizing ammonia that masks out these lower clouds from view.
The only spacecraft to have descended into Jupiter's atmosphere and take
scientific measurements is the
Galileo probe (see
mission). It sent an atmospheric probe into Jupiter upon arrival in
1995, then itself
entered Jupiter's atmosphere and burned up in
The Great Red Spot
The Great Red Spot is a persistent
storm on the
Jupiter, 22° south of the equator, which has lasted at least 340 years. The
storm is large enough to be visible through Earth-based
It was probably first observed by Giovanni Domenico Cassini, who described it
This dramatic view of Jupiter's Great Red Spot and its surroundings was
Voyager 1 on
25, 1979, when
the spacecraft was 9.2 million km (5.7 million miles) from Jupiter. Cloud
details as small as 160 km (100 miles) across can be seen here. The colorful,
wavy cloud pattern to the left of the Red Spot is a region of extraordinarily
complex and variable wave motion. To give a sense of Jupiter's scale, the white
oval storm directly below the Great Red Spot is approximately the same diameter
The oval object
counterclockwise, with a
of about 6 days.
The Great Red Spot's
are 24–40,000 km × 12–14,000 km. It is large enough to contain two or three
planets of Earth's size.
The tops of this storm is about 8 km above the surrounding cloudtops.
Jupiter's Great Red Spot
Storms such as this are not uncommon within the
Jupiter also has white ovals and brown ovals, which are lesser unnamed storms.
White ovals tend to consist of relatively
cool clouds within
the upper atmosphere. Brown ovals are warmer and located within the "normal
cloud layer". Such storms can last hours or
Before the Voyager missions, astronomers were uncertain of the nature of
Jupiter's Great Red Spot. Many believed it to be either a solid or a liquid
feature on the planet's surface as this appears consistent with the observable
However, even before Voyager proved that the feature was a storm, there was
strong evidence that the spot cannot be associated with any deeper feature on
the planet's surface, as it has been proven that the Spot rotates differentially
with respect to the rest of the atmosphere, sometimes faster and sometimes more
slowly, so that during its recorded history it has traveled several times around
the planet with regard to any possible fixed rotational marker below it.
Recent examination of Jupiter's surface by a NASA research team using the
Hubble telescope has shown that several smaller storms located near to the Giant
Red Spot have, in the last twelve months, amalgamated, increased in intensity
and changed colour from white to red.
This data on Oval BA, nicknamed Red Spot Jnr.
was published in the astronomical journal Icarus by planetary scientist Amy
Simon-Miller in October 2006. Further investigations using spectroscopy have
been delayed due to the movement of Jupiter behind the Sun and it is yet to be
verified if the phenomena is caused by increased wind speed, comparable to the
400 mph speeds in the larger anomaly, drawing similar materials from deeper in
the atmosphere and exposing them to sunlight.
Jupiter has a faint
planetary ring system composed of three main components: an inner
particles known as the
halo, a relatively bright main ring, and an outer "gossamer" ring.
The main ring is probably made of material ejected from the satellites
Metis. Material that would normally fall back to the moon is pulled into
Jupiter's orbit due to its strong gravitational pull. The orbit of the material
decays towards Jupiter and new material is added by additional impacts.
In a similar way, the moons
Amalthea probably produce the two distinct components of the gossamer ring.
This planet's broad magnetic field is 14 times as strong as the Earth's,
ranging from 4.2
gauss at the equator to 10–14 gauss at the poles, making it the strongest in
the solar system (with the exception of
This field is believed to be generated by
currents within the metallic hydrogen core. The field traps a sheet of
particles from the
generating a highly energetic magnetosphere around the planet that extends
outward to a radius of 150–200 times the radius of Jupiter. Electrons from this
plasma sheet ionize the torus of
sulfur dioxide generated by the
activity on the moon Io. Hydrogen particles from Jupiter's atmosphere are also
trapped in the magnetosphere. Electrons within the magnetosphere generate a
strong radio signature that produces bursts in the range of 0.6–30
Exploration of Jupiter
Since 1973 a number of automated spacecraft have visited Jupiter. Flights to
other planets within the Solar System are accomplished at a cost in
is described by the net change in velocity of the spacecraft, or
Reaching Jupiter from Earth requires a delta-v of 9.2 km/s,
which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit.
gravity assists through planetary
flybys can be
used to reduce the energy required to reach Jupiter, albeit at the cost of a
significantly longer flight duration.
||December 3, 1973
||December 4, 1974
||March 5, 1979
||August 18, 1999
Beginning in 1973, several spacecraft have performed planetary fly-by
maneuvers that brought them within observation range of Jupiter. Pioneer 10
obtained the first ever close up images of Jupiter and the
Galilean moons, studied its atmosphere, detected its magnetic field,
observed its radiation belts and found that Jupiter is mainly liquid.
Six years later the Voyager missions vastly improved the understanding of
Galilean moons and discovered Jupiter's rings. They also took the first
close up images of the planet's atmosphere.
The next mission to encounter Jupiter, the Ulysses solar probe,
performed a fly-by maneuver in order to attain a polar orbit around the Sun.
During this pass the probe conducted studies on Jupiter's magnetosphere.
However, since there are no cameras onboard the probe, no images were taken. A
second fly-by six years later was at a much greater distance.
In 2000, the Cassini probe, en route to
Saturn, flew by
Jupiter and provided some of the highest-resolution images ever made of the
19, 2000, the
Cassini spacecraft, captured a very low resolution image of the moon
Himalia, but it was too distant to show any surface details.
Horizons probe, en route to
Pluto, will flyby
Jupiter for a gravity assist. Closest approach will be
28, 2007. While
at Jupiter, New Horizon's instruments will refine the orbits of Jupiter's inner
Amalthea. The probe's cameras will measure plasma output from volcanoes on
and study all four Gallilean moons in detail.
Imaging of the Jovian system began
During the period
July 16 to
1994, over twenty
fragments from the
comet Shoemaker-Levy 9 hit Jupiter's southern hemisphere, providing the
first direct observation of a collision between two solar system objects.
Although not a probe from Earth, the impact did provide data on the composition
of Jupiter's atmosphere.
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
So far the only spacecraft to orbit Jupiter is the
Galileo orbiter, which went into orbit around Jupiter on
1995. It orbited
the planet for over seven years, conducting multiple flybys of all of the
Galilean moons and
Amalthea. The spacecraft also witnessed the impact of
Comet Shoemaker-Levy 9 as it approached Jupiter in 1994, giving a unique
vantage point for the event. However, while the information gained about the
Jovian system from Galileo was extensive, its originally-designed
capacity was limited by the failed deployment of its high-gain radio
An atmospheric probe was released from the spacecraft in July, 1995, entering
the planet's atmosphere on
It parachuted through 150 km of the atmosphere, collecting data for 57.6
minutes, before being crushed by the pressure to which it was subjected by that
time (about 22 times Earth normal, at a temperature of 153 oC).
 It would have melted thereafter, and possibly vaporized. The Galileo
orbiter itself experienced a more rapid version of the same fate when it was
deliberately steered into the planet on
September 21, 2003
at a speed of over 50 km/s, in order to avoid any possibility of it crashing
into and possibly contaminating
NASA is planning a mission to study Jupiter in detail from a
Juno, the spacecraft is planned to launch by 2010.
Because of the possibility of a liquid ocean on Jupiter's moon
Europa, there has been great interest to study the icy moons in detail. A
mission proposed by NASA was dedicated to study them. The
JIMO (Jupiter Icy Moons Orbiter) was expected to be launched sometime after
2012. However, the mission was deemed too ambitious and its funding was
Jupiter has at least 63 moons. For a complete listing of these moons, please
Jupiter's natural satellites. For a timeline of their discovery dates, see
Timeline of discovery of Solar System planets and their natural satellites.
The four large moons, known as the "Galilean
The orbits of Io, Europa, and Ganymede, the largest moon in the solar system,
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
gravitational effects of the three moons to distort their orbits into
elliptical shapes, since each moon receives an extra tug from its neighbours at
the same point in every orbit it makes.
tidal force from Jupiter, on the other hand, works to circularize their
This constant tug of war causes regular flexing of the three moons' shapes, with
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.
Before the discoveries of the Voyager missions, Jupiter's moons were arranged
neatly into four groups of four. Since then, the large number of new small outer
moons has complicated this picture. There are now thought to be six main groups,
although some are more distinct than others. A basic division is between the
eight inner regular moons with nearly circular orbits near the plane of
Jupiter's equator, which are believed to have formed with Jupiter, and an
unknown number of small irregular moons, with elliptical and inclined orbits,
which are believed to be captured asteroids or fragments of captured asteroids.
It is thought that the groups of outer moons may each have a common origin,
perhaps as a larger moon or captured body that broke up.
It is considered highly unlikely that there is any Earth-like
life on Jupiter, as there is little water in the atmosphere and any possible
solid surface deep within Jupiter would be under extraordinary pressures.
However, in 1976,
Edwin Ernest Salpeter) that
life could evolve in Jupiter's upper atmosphere. Sagan and Salpeter based this
hypothesis on the ecology of terrestrial seas which have simple
photosynthetic plankton at
the top level, fish
at lower levels feeding on these creatures, and marine
which hunt the fish. The Jovian equivalents Sagan and Salpeter hypothesized were
"sinkers", "floaters", and "hunters". The "sinkers" would be plankton-like
organisms which fall through the atmosphere, existing just long enough that they
can reproduce in the time they are kept afloat by convection. The "floaters"
would be giant bags of gas functioning along the lines of hot air balloons,
using their own metabolism (feeding off sunlight and free molecules) to keep
their gas warm. The "hunters" would be almost
creatures, using jets of gas to propel themselves into "floaters" and consume
In addition to its moons, Jupiter's gravitational field controls numerous
which have settled into the regions of the
Lagrangian points preceding and following Jupiter in its orbit around the
sun. These are known as the
Trojan asteroids, and are divided into
Trojan "camps" to commemorate the
first of these,
Achilles, was discovered by
Max Wolf in
1906; since then
hundreds more have been discovered. The largest is