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Jupiter
Table of Contents
Jupiter
Table of Contents
* Introduction & Top Questions
*
Basic astronomical data
* The atmosphere
* The clouds and the Great Red Spot
* Nature of the Great Red Spot
* Cloud composition
* Atmospheric characteristics
* Proportions of constituents
* Temperature and pressure
* Other likely atmospheric constituents
* Collisions with comets and asteroids
* Radio emission
*
The magnetic field and magnetosphere
*
The auroras
*
The interior
* Jupiter’s moons and ring
* The Galilean satellites
* Callisto
* Ganymede
* Europa
* Io
* Other satellites
* The ring
* Origin of the Jovian system
* Early history of Jupiter
* Early history of the satellites
References & Edit History Related Topics
Images, Videos & Interactives
For Students
Jupiter summary
Quizzes
Astronomy and Space Quiz
Science Quiz
Space Odyssey
Planets and the Earth’s Moon
Brightest Star in the Solar System
Related Questions
* What is Jupiter made up of?
* What is Robert Hooke famous for?
* How has Galileo influenced science?
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JUPITER
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Written by
Tobias Chant Owen
Professor of Astronomy, University of Hawaii at Manoa, Honolulu. Coauthor of The
Planetary System; The Search for Life in the Universe; and numerous research
articles.
Tobias Chant Owen
Fact-checked by
The Editors of Encyclopaedia Britannica
Encyclopaedia Britannica's editors oversee subject areas in which they have
extensive knowledge, whether from years of experience gained by working on that
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Last Updated: Dec 26, 2023 • Article History
Table of Contents
Top Questions
WHAT IS THE PERIOD OF REVOLUTION OF JUPITER?
Jupiter takes nearly 12 Earth years to orbit the Sun, and it rotates once about
every 10 hours, more than twice as fast as Earth.
WHEN WAS JUPITER'S RING DISCOVERED?
The existence of Jupiter's ring was first suggested in 1974, as a result of
findings from the Pioneer 10 spacecraft as it approached the planet. The ring
was verified in 1979 by the first Voyager spacecraft when it crossed the
planet’s equatorial plane.
IS JUPITER THE LARGEST PLANET IN THE SOLAR SYSTEM?
Jupiter is the most massive planet in the solar system. It has an equatorial
diameter of about 143,000 km (88,900 miles).
WHAT IS JUPITER MADE UP OF?
Jupiter is composed primarily of hydrogen and helium. Under equilibrium
conditions, the abundant chemically active elements are all expected to combine
with hydrogen.Thus, during earlier study of Jupiter, it was surmised that
methane, ammonia, water, and hydrogen sulfide would be present. Except for
hydrogen sulfide, all these compounds have been found by spectroscopic
observations from Earth.
photo of Jupiter taken by Voyager 1
Photograph of Jupiter taken by Voyager 1 on February 1, 1979, at a range of 32.7
million km (20.3 million miles). Prominent are the planet's pastel-shaded cloud
bands and Great Red Spot (lower centre).(more)
Jupiter, the most massive planet of the solar system and the fifth in distance
from the Sun. It is one of the brightest objects in the night sky; only the
Moon, Venus, and sometimes Mars are more brilliant. Jupiter is designated by the
symbol ♃.
When ancient astronomers named the planet Jupiter for the Roman ruler of the
gods and heavens (also known as Jove), they had no idea of the planet’s true
dimensions, but the name is appropriate, for Jupiter is larger than all the
other planets combined. It takes nearly 12 Earth years to orbit the Sun, and it
rotates once about every 10 hours, more than twice as fast as Earth; its
colourful cloud bands can be seen with even a small telescope. It has a narrow
system of rings and 92 known moons, one larger than the planet Mercury and three
larger than Earth’s Moon. Some astronomers speculate that Jupiter’s moon Europa
may be hiding an ocean of warm water—and possibly even some kind of life—beneath
an icy crust.
Jupiter has an internal heat source; it emits more energy than it receives from
the Sun. The pressure in its deep interior is so high that the hydrogen there
exists in a fluid metallic state. This giant has the strongest magnetic field of
any planet, with a magnetosphere so large that, if it could be seen from Earth,
its apparent diameter would exceed that of the Moon. Jupiter’s system is also
the source of intense bursts of radio noise, at some frequencies occasionally
radiating more energy than the Sun. Despite all its superlatives, however,
Jupiter is made almost entirely of only two elements, hydrogen and helium, and
its mean density is not much more than the density of water.
crescent view of Jupiter
Crescent view of Jupiter, a composite of three images taken by Voyager 1 on
March 24, 1979.(more)
View Jupiter's images captured from the Long Range Reconnaissance Imager (LORRI)
aboard the New Horizons spacecraft
View of Jupiter created from images taken by the Long Range Reconnaissance
Imager (LORRI) aboard the New Horizons spacecraft.(more)
See all videos for this article
Knowledge about the Jovian system grew dramatically after the mid-1970s as a
result of explorations by three spacecraft missions—Pioneers 10 and 11 in
1973–74, Voyager 1 and 2 in 1979, and the Galileo orbiter and probe, which
arrived at Jupiter in December 1995. The Pioneer spacecraft served as scouts for
the Voyagers, showing that the radiation environment of Jupiter was tolerable
and mapping out the main characteristics of the planet and its environment. The
greater number and increased sophistication of the Voyager instruments provided
so much new information that it was still being analyzed when the Galileo
mission began. The previous missions had all been flybys, but Galileo released a
probe into Jupiter’s atmosphere and then went into orbit about the planet for
intensive investigations of the entire system until September 2003. In July
2016, the Juno orbiter arrived at Jupiter for a mission expected to last two
years. Other looks at the Jovian system were provided in late 2000 and early
2001 by the flyby of the Cassini spacecraft on its way to Saturn and in 2007 by
the flyby of the New Horizons spacecraft on its way to Pluto. Observations of
the impacts of the fragmented nucleus of Comet Shoemaker-Levy 9 with Jupiter’s
atmosphere in 1994 also yielded information about its composition and structure.
Britannica Quiz
Giants of Our Solar System
BASIC ASTRONOMICAL DATA
Jupiter has an equatorial diameter of about 143,000 km (88,900 miles) and orbits
the Sun at a mean distance of 778 million km (483 million miles). The table
shows additional physical and orbital data for Jupiter. Of special interest are
the planet’s low mean density of 1.33 grams per cubic cm—in contrast with
Earth’s 5.52 grams per cubic cm—coupled with its large dimensions and mass and
short rotation period. The low density and large mass indicate that Jupiter’s
composition and structure are quite unlike those of Earth and the other inner
planets, a deduction that is supported by detailed investigations of the giant
planet’s atmosphere and interior.
Planetary data for Jupiter *Time required for the planet to return to the same
position in the sky relative to the Sun as seen from Earth. **Calculated for the
altitude at which 1 bar of atmospheric pressure is exerted. mean distance from
Sun 778,340,821 km (5.2 AU) eccentricity of orbit 0.048 inclination of orbit to
ecliptic 1.3° Jovian year (sidereal period of revolution) 11.86 Earth years
visual magnitude at mean opposition −2.70 mean synodic period* 398.88 Earth days
mean orbital velocity 13.1 km/sec equatorial radius** 71,492 km polar radius**
66,854 km mass 18.98 × 1026 kg mean density 1.33 g/cm3 gravity** 2,479 cm/sec2
escape velocity 60.2 km/sec rotation periods System I (±10° from equator) 9 hr
50 min 30 sec System II (higher latitudes) 9 hr 55 min 41 sec System III
(magnetic field) 9 hr 55 min 29 sec inclination of equator to orbit 3.1°
dimensions of Great Red Spot 20,000 × 12,000 km magnetic field strength at
equator 4.3 gauss number of known moons 66 planetary ring system 1 main ring; 3
less-dense components
Three rotation periods, all within a few minutes of each other, have been
established. The two periods called System I (9 hours 50 minutes 30 seconds) and
System II (9 hours 55 minutes 41 seconds) are mean values and refer to the speed
of rotation at the equator and at higher latitudes, respectively, as exhibited
by features observed in the planet’s visible cloud layers. Jupiter has no solid
surface; the transition from the gaseous atmosphere to the fluid interior occurs
gradually at great depths. Thus the variation in rotation period at different
latitudes does not imply that the planet itself rotates with either of these
mean velocities. In fact, the true rotation period of Jupiter is System III (9
hours 55 minutes 29 seconds). This is the period of rotation of Jupiter’s
magnetic field, first deduced from Earth-based observations at radio wavelengths
(see below Radio emission) and confirmed by direct spacecraft measurements. This
period, which has been constant for 30 years of observation, applies to the
massive interior of the planet, where the magnetic field is generated.
THE ATMOSPHERE
THE CLOUDS AND THE GREAT RED SPOT
computer-generated composite of Jupiter
Computer-generated composite of Jupiter, showing the entire planet's visible
surface and its characteristic cloud bands. The four small dark ovals lined up
in the upper centre of the image may be gaps in the upper atmosphere, opening to
reveal cloud layers below. The Great Red Spot appears in the lower right. The
composite is based on 10 colour images taken by Voyager 1 on February 1,
1979.(more)
computer-generated visualization of Jupiter's equatorial cloud layers
Computer-generated visualization of a portion of Jupiter's equatorial cloud
layers, simulating a view from between layers. Ordinarily, when seen from space,
Jupiter's cloud surfaces have a topographically flat appearance. This
false-colour image combines data from Galileo spacecraft observations made at
three wavelengths of infrared light, which are absorbed at different levels of
the atmosphere and thus provide information about cloud heights that can be used
to add surface relief. The image reduces the more complex true cloud layer into
a simple model with lower and upper decks. Visible just above the lower deck is
a small cloud formation (rendered in light blue). To its left (in reddish
purple) is a “hot spot,” a hole in the lower cloud layer similar to one in which
the Galileo probe entered on December 7, 1995.(more)
Even a modest telescope can show much detail on Jupiter. The region of the
planet’s atmosphere that is visible from Earth contains several different types
of clouds that are separated both vertically and horizontally. Changes in these
cloud systems can occur over periods of a few hours, but an underlying pattern
of latitudinal currents has maintained its stability for decades. It has become
traditional to describe the appearance of the planet in terms of a standard
nomenclature for its alternating dark bands, called belts, and bright bands,
called zones. The underlying currents, however, seem to have a greater
persistence than this pattern. For example, the south equatorial belt has faded
away several times and has even totally disappeared (most recently in 2010),
only to reappear months or years later.
false-colour mosaic of Jupiter's northern hemisphere
False-colour mosaic of a part of Jupiter's northern hemisphere, made from images
taken by the Galileo spacecraft on April 3, 1997. North is at the top. The more
conspicuous features include alternating bands of eastward- and westward-moving
clouds, white ovals, dark spots, and turbulent vortices. The view is one of the
first to show different layers in Jupiter's atmosphere: haze over
upper-atmosphere cloud breaks is represented in dark purple, thin high clouds in
light blue, thick high clouds in white, and clouds lower in the atmosphere in
reddish hues. (more)
The close-up views of Jupiter transmitted to Earth by spacecraft reveal a
variety of cloud forms, including many elliptical features reminiscent of
cyclonic and anticyclonic storm systems on Earth. All these systems are in
motion, appearing and disappearing on time scales that vary with their sizes and
locations. Also observed to vary are the pastel shades of various colours
present in the cloud layers—from the tawny yellow that seems to characterize the
main layer, through browns and blue-grays, to the well-known salmon-coloured
Great Red Spot, Jupiter’s largest, most prominent, and longest-lived feature.
Chemical differences in cloud composition, which astronomers presume to be the
cause of the variations in colour, evidently accompany the vertical and
horizontal segregation of the cloud systems.
false-colour mosaic of the Great Red Spot
False-colour mosaic of two of the long-lived white ovals south of the Great Red
Spot, assembled from images taken by the Galileo spacecraft on February 19,
1997. The colours represent the relative altitude and density of different
clouds in Jupiter's atmosphere. Light blue clouds, such as those at the centres
of the ovals, are high and thin; white clouds surrounding the blue are at the
same altitude but are thicker; and the dark purple over the ovals is high haze
reaching into the stratosphere.(more)
Jovian meteorology can be compared with the global circulation of Earth’s
atmosphere. On Earth huge spiral cloud systems often stretch over many degrees
of latitude and are associated with motion around high- and low-pressure
regions. These cloud systems are much less zonally confined than the cloud
systems on Jupiter and move in latitude as well as longitude. Local weather on
Earth is often closely tied to the local environment, which in turn is
determined by the varied nature of the planet’s surface.
Jupiter: south pole
Jupiter's south pole as seen by the Juno spacecraft.(more)
Jupiter has no solid surface—hence, no topographic features—and the planet’s
large-scale circulation is dominated by latitudinal currents. The lack of a
solid surface with physical boundaries and regions with different heat
capacities makes the persistence of these currents and their associated cloud
patterns all the more remarkable. The Great Red Spot, for example, moves in
longitude with respect to all three of the planet’s rotation systems, yet it
does not move in latitude. The white ovals found at a latitude just south of the
Great Red Spot exhibit similar behaviour; white ovals of this size are found
nowhere else on the planet. The dark brown clouds, evidently holes in the tawny
cloud layer, are found almost exclusively near 18° N latitude. The strongest
thermal emission is detected from blue-gray or purple areas that occur in the
equatorial region of the planet. Observations from Juno showed that the poles
are covered in swirling Earth-sized storms.
NATURE OF THE GREAT RED SPOT
Great Red Spot
A true-colour image of Jupiter's Great Red Spot taken by the Juno
spacecraft.(more)
The true nature of Jupiter’s unique Great Red Spot was still unknown at the
start of the 21st century, despite extensive observations from the Voyager,
Galileo, and Juno spacecrafts. On a planet whose cloud patterns have lifetimes
often counted in days, the Great Red Spot has been continuously observed since
1878 and may even be the same storm that was observed from 1665 to 1713. From
its maximum extent of about 48,000 km (30,000 miles) in the late 19th century,
the spot has been shrinking, and since 2012 the spot, once decidedly oval, has
become more circular and has been shrinking at an accelerated rate of 900 km
(580 miles) per year. Its present size is about 16,350 km (10,159 miles)
wide—large enough to accommodate Earth easily. These huge dimensions are
probably responsible for the feature’s longevity and possibly for its distinct
colour.
Great Red Spot
Jupiter's Great Red Spot (top right) and the surrounding region, as seen from
Voyager 1 on March 1, 1979. Below the spot is one of the large white ovals
associated with the feature.(more)
The rotation period of the Great Red Spot around the planet does not match any
of Jupiter’s three rotation periods. It shows a variability that has not been
successfully correlated with other Jovian phenomena. Voyager observations
revealed that the material within the spot circulates in a counterclockwise
direction once every seven days, corresponding to superhurricane-force winds of
400 km (250 miles) per hour at the periphery. The Voyager images also recorded a
large number of interactions between the Great Red Spot and much smaller
disturbances moving in the current at the same latitude. The interior of the
spot is remarkably tranquil, with no clear evidence for the expected upwelling
(or divergence) of material from lower depths.
Jupiter's Great Red Spot
Jupiter's Great Red Spot and its surroundings, photographed by Voyager 1,
February 25, 1979. Included are the white ovals, observed since the 1930s, and
immense areas of turbulence to the left of the Great Red Spot.(more)
The Great Red Spot, therefore, appears to be a huge anticyclone, a vortex or
eddy whose diameter is presumably accompanied by a great depth that allows the
feature to reach well below and well above the main cloud layers. The Red Spot
is heating Jupiter’s upper atmosphere from below and making it hundreds of
degrees hotter than would be expected from solar heating alone. The spot’s lower
extension remains to be observed.
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* Origin of the Jovian system
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* Live Science - Jupiter: Facts about the king of the planets
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* The Planetary Society - Jupiter, the planet with a planetary system of its
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* National Geographic - Science - Jupiter
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