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Jupiter
Jupiter is the largest planet in
the solar system. Its diameter is 88,846 miles (142,984 kilometers), more than
11 times that of Earth, and about one-tenth that of the sun. It would take more
than 1,000 Earths to fill up the volume of the giant planet. When viewed from
Earth, Jupiter appears brighter than most stars. It is usually the second
brightest planet -- after Venus.
Jupiter is the fifth planet from
the sun. Its mean (average) distance from the sun is about 483,780,000 miles
(778,570,000 kilometers), more than five times Earth's distance. Ancient
astronomers named Jupiter after the king of the Roman gods.
Astronomers have studied Jupiter
with telescopes based on Earth and aboard artificial satellites in orbit around
Earth. In addition, the United States has sent six space probes (crewless
exploratory craft) to Jupiter.
Astronomers witnessed a
spectacular event in July 1994, when 21 fragments of a comet named
Shoemaker-Levy 9 crashed into Jupiter's atmosphere. The impacts caused
tremendous explosions, some scattering debris over areas larger than the
diameter of Earth.
Physical features of Jupiter
Jupiter is a giant ball of gas
and liquid with little, if any, solid surface. Instead, the planet's surface is
composed of dense red, brown, yellow, and white clouds. The clouds are arranged
in light-colored areas called zones and darker regions called belts that circle
the planet parallel to the equator.
Orbit and rotation
Jupiter travels around the sun in
a slightly elliptical (oval-shaped) orbit. The planet completes one orbit in
4,333 Earth days, or almost 12 Earth years.
As Jupiter orbits the sun, the
planet rotates on its axis, an imaginary line through its center. The axis is
tilted about 3¡. Scientists measure tilt relative to a line at a right angle to
the orbital plane, an imaginary surface touching all points of the orbit.
Jupiter rotates faster than any
other planet. It takes 9 hours 56 minutes to spin around once on its axis,
compared with 24 hours for Earth. Scientists cannot measure the rotation of the
interior of the giant planet directly, so they have calculated the speed from
indirect measurements. They first calculated the speed using an average of the
speeds of the visible clouds that move with interior currents, except for a more
rapid zone near the equator.
Jupiter sends out radio waves
strong enough to be picked up by radio telescopes on Earth. Scientists now
measure these waves to calculate Jupiter's rotational speed. The strength of the
waves varies under the influence of Jupiter's magnetic field in a pattern that
repeats every 9 hours 56 minutes. Because the magnetic field originates in
Jupiter's core, this variation shows how fast the plant's interior spins.
Jupiter's rapid rotation makes it
bulge at the equator and flatten at the poles. The planet's diameter is about 7
percent larger at the equator than at the poles.
Mass and density
Jupiter is heavier than any other
planet. Its mass (quantity of matter) is 318 times larger than that of Earth.
Although Jupiter has a large mass, it has a relatively low density. Its density
averages 1.33 grams per cubic centimeter, slightly more than the density of
water. The density of Jupiter is about 1/4 that of Earth. Because of Jupiter's
low density, astronomers believe that the planet consists primarily of hydrogen
and helium, the lightest elements. Earth, on the other hand, is made up chiefly
of metals and rock. Jupiter's mix of chemical elements resembles that of the
sun, rather than that of Earth.
Jupiter may have a core made up
of heavy elements. The core may be of about the same chemical composition as
Earth, but 20 or 30 times more massive.
The force of gravity at the
surface of Jupiter is up to 2.4 times stronger than on Earth. Thus, an object
that weighs 100 pounds on Earth would weigh as much as 240 pounds on Jupiter.
The atmosphere of Jupiter is
composed of about 86 percent hydrogen, 14 percent helium, and tiny amounts of
methane, ammonia, phosphine, water, acetylene, ethane, germanium, and carbon
monoxide. The percentage of hydrogen is based on the number of hydrogen
molecules in the atmosphere, rather than on their total mass. Scientists have
calculated these amounts from measurements taken with telescopes and other
instruments on Earth and aboard spacecraft.
These chemicals have formed
colorful layers of clouds at different heights. The highest white clouds in the
zones are made of crystals of frozen ammonia. Darker, lower clouds of other
chemicals occur in the belts. At the lowest levels that can be seen, there are
blue clouds. Astronomers had expected to detect water clouds about 44 miles (70
kilometers) below the ammonia clouds. However, none have been discovered at any
level.
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The
planet Jupiter's Great Red Spot is a huge mass of swirling gas. At its
widest, it is about three times the diameter of the Earth. Image credit:
NASA
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Jupiter's most outstanding surface
feature is the Great Red Spot, a swirling mass of gas resembling a hurricane.
The widest diameter of the spot is about three times that of Earth. The color of
the spot usually varies from brick-red to slightly brown. Rarely, the spot fades
entirely. Its color may be due to small amounts of sulfur and phosphorus in the
ammonia crystals.
The edge of the Great Red Spot
circulates at a speed of about 225 miles (360 kilometers) per hour. The spot
remains at the same distance from the equator but drifts slowly east and west.
The zones, belts, and the Great
Red Spot are much more stable than similar circulation systems on Earth. Since
astronomers began to use telescopes to observe these features in the late
1600's, the features have changed size and brightness but have kept the same
patterns.
Temperature
The temperature at the top of
Jupiter's clouds is about -230 degrees F (-145 degrees C). Measurements made by
ground instruments and spacecraft show that Jupiter's temperature increases with
depth below the clouds. The temperature reaches 70 degrees F (21 degrees C) --
"room temperature" -- at a level where the atmospheric pressure is
about 10 times as great as it is on Earth. Scientists speculate that if Jupiter
has any form of life, the life form would reside at this level. Such life would
need to be airborne, because there is no solid surface at this location on
Jupiter. Scientists have discovered no evidence for life on Jupiter.
Near the planet's center, the
temperature is much higher. The core temperature may be about 43,000 degrees F
(24,000 degrees C) -- hotter than the surface of the sun.
Jupiter is still losing the heat
produced when it became a planet. Most astronomers believe that the sun, the
planets, and all the other bodies in the solar system formed from a spinning
cloud of gas and dust. The gravitation of the gas and dust particles packed them
together into dense clouds and solid chunks of material. By about 4.6 billion
years ago, the material had squeezed together to form the various bodies in the
solar system. The compression of material produced heat. So much heat was
produced when Jupiter formed that the planet still radiates about twice as much
heat into space as it receives from sunlight.
Magnetic field
Like Earth and many other
planets, Jupiter acts like a giant magnet. The force of its magnetism extends
far into space in a region surrounding the planet called its magnetic field.
Jupiter's magnetic field is about 14 times as strong as Earth's, according to
measurements made by spacecraft. Jupiter's magnetic field is the strongest in
the solar system, except for fields associated with sunspots and other small
regions on the sun's surface.
Scientists do not fully
understand how planets produce magnetic fields. They suspect, however, that the
movement of electrically charged particles in the interior of planets generates
the fields. Jupiter's field would be so much stronger than Earth's because of
Jupiter's greater size and faster rotation.
Jupiter's magnetic field traps
electrons, protons, and other electrically charged particles in radiation belts
around the planet. The particles are so powerful that they can damage
instruments aboard spacecraft operating near the planet.
Within a region of space called
the magnetosphere, Jupiter's magnetic field acts as a shield. The field protects
the planet from the solar wind, a continuous flow of charged particles from the
sun. Most of these particles are electrons and protons traveling at a speed of
about 310 miles (500 kilometers) per second. The field traps the charged
particles in the radiation belts. The trapped particles enter the magnetosphere
near the poles of the magnetic field. On the side of the planet away from the
sun, the magnetosphere stretches out into an enormous magnetic tail, often
called a magnetotail, that is at least 435 million miles (700 million
kilometers) long.
Radio waves given off by Jupiter
reach radio telescopes on Earth in two forms -- bursts of radio energy and
continuous radiation. Strong bursts occur when Io, the closest of Jupiter's four
large moons, passes through certain regions in the planet's magnetic field.
Continuous radiation comes from Jupiter's surface as well as from high-energy
particles in the radiation belts.
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Callisto,
a moon of Jupiter, is covered with craters produced when asteroids and
comets struck its icy surface. Beneath the surface may be an ocean of
salty liquid water. Image credit: NASA
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Satellites
Jupiter has 16 satellites that
measure at least 6 miles (10 kilometers) in diameter. It also has many smaller
satellites. Jupiter's four largest satellites, in order of their distance from
Jupiter, are Io, Europa, Ganymede, and Callisto. These four moons are called the
Galilean satellites. The Italian astronomer Galileo discovered them in 1610 with
one of the earliest telescopes.
Io has many active volcanoes,
which produce gases containing sulfur. The yellow-orange surface of Io probably
consists largely of solid sulfur that was deposited by the eruptions. Europa
ranks as the smallest of the Galilean satellites, with a diameter of 1,945 miles
(3,130 kilometers). Europa has a smooth, cracked, icy surface.
The largest Galilean satellite is
Ganymede, with a diameter of 3,273 miles (5,268 kilometers). Ganymede is larger
than the planet Mercury. Callisto, with a diameter of 2,986 miles (4,806
kilometers), is slightly smaller than Mercury. Ganymede and Callisto appear to
consist of ice and some rocky material. The two satellites have many craters.
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Ganymede,
a moon of Jupiter, has craters and cracks on its surface. Asteroids and
comets that hit Ganymede made the craters. The cracks are due to
expansion and contraction of the surface. Image credit: NASA
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Jupiter's remaining satellites are
much smaller than the Galilean moons. Amalthea and Himalia are the next largest.
Potato-shaped Amalthea is about 163 miles (262 kilometers) in its long
dimension. Himalia is 106 miles (170 kilometers) in diameter. Most of the
remaining satellites were discovered by astronomers using large telescopes on
Earth. Scientists discovered Metis and Adrastea in 1979 by studying pictures
that had been taken by the Voyager spacecraft.
Rings
Jupiter has three thin rings
around its equator. They are much fainter than the rings of Saturn. Jupiter's
rings appear to consist mostly of fine dust particles. The main ring is about 20
miles (30 kilometers) thick and more than 4,000 miles (6,400 kilometers) wide.
It circles the planet inside the orbit of Amalthea.
The impact of Comet
Shoemaker-Levy 9
In March 1993, astronomers Eugene
Shoemaker, Carolyn Shoemaker, and David H. Levy discovered a comet near Jupiter.
The comet, later named Shoemaker-Levy 9, probably once orbited the sun
independently, but had been pulled by Jupiter's gravity into an orbit around the
planet. When the comet was discovered, it had broken into 21 pieces. The comet
probably had broken apart when it passed close to Jupiter.
Calculations based on the comet's
location and velocity showed that the fragments would crash into Jupiter's
atmosphere in July 1994. Scientists hoped to learn much about the effects of a
collision between a planet and a comet.
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Scars
from the crash of Comet Shoemaker-Levy 9 appear on Jupiter's surface as
a series of maroon blotches in this photo. The comet broke into 21
pieces before it hit Jupiter in 1994. Image credit: Hubble Space
Telescope Comet Team and NASA
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Astronomers at all the major
telescopes on Earth turned their instruments toward Jupiter at the predicted
collision times. Scientists also observed Jupiter with the powerful Hubble Space
Telescope, which is in orbit around Earth; and the remotely controlled space
probe Galileo, which was on its way to Jupiter.
The fragments fell on the back
side of Jupiter as viewed from Earth and the Hubble Space Telescope. But the
rotation of Jupiter carried the impact sites around to the visible side after
less than half an hour. Scientists estimate that the largest fragments were
about 0.3 to 2.5 miles (0.5 to 4 kilometers) in diameter. The impacts were
directly observable from Galileo, which was within about 150 million miles (240
million kilometers) from Jupiter. However, damage to certain of the probe's
instruments limited its ability to record and send data.
The impacts caused large
explosions, probably due to the compression, heating, and rapid expansion of
atmospheric gases. The explosions scattered comet debris over large areas, some
with diameters larger than that of Earth. The debris gradually spread into a
dark haze of fine material that remained suspended for several months in
Jupiter's upper atmosphere. If a similar comet ever collided with Earth, it
might produce a haze that would cool the atmosphere and darken the planet by
absorbing sunlight. If the haze lasted long enough, much of Earth's plant life
could die, along with the people and animals that depend on plants.
Flights to Jupiter
The United States has sent six
space probes to Jupiter: (1) Pioneer 10, (2) Pioneer-Saturn, (3) Voyager 1, (4)
Voyager 2, (5) Ulysses, and (6) Galileo.
Pioneer 10 was launched in 1972
and flew within 81,000 miles (130,000 kilometers) of Jupiter on Dec. 3, 1973.
The probe revealed the severe effects of Jupiter's radiation belt on spacecraft.
Pioneer 10 also reported the amount of hydrogen and helium in the planet's
atmosphere. In addition, the probe discovered that Jupiter has an enormous
magnetosphere.
Pioneer-Saturn flew within 27,000
miles (43,000 kilometers) of Jupiter in December 1974. The craft provided
close-up photographs of Jupiter's polar regions and data on the Great Red Spot,
the magnetic field, and atmospheric temperatures.
Voyager 1 and Voyager 2 flew past
Jupiter in March and July 1979, respectively. These craft carried more sensitive
instruments than did the Pioneers, and transmitted much more information.
Astronomers used photographs taken by the Voyagers to make the first detailed
maps of the Galilean satellites. The Voyagers also revealed sulfur volcanoes on
Io, discovered lightning in Jupiter's clouds, and mapped flow patterns in the
cloud bands.
Ulysses was launched in October
1990 and passed by Jupiter in February 1992. The European Space Agency, an
organization of Western European nations, had built the probe mainly to study
the sun's polar regions. Scientists used the tremendous gravitational force of
Jupiter to put Ulysses into an orbit that would take it over the sun's polar
regions. As Ulysses passed by Jupiter, it gathered data indicating that the
solar wind has a much greater effect on Jupiter's magnetosphere than earlier
measurements had suggested.
Galileo began its journey to
Jupiter in October 1989. The craft released an atmospheric probe in July 1995.
In December 1995, the probe plunged into Jupiter's atmosphere. The probe
penetrated deep into the cloud layers and measured the amount of water and other
chemicals in the atmosphere. Also in December 1995, Galileo went into orbit
around Jupiter. Over the next several years, the craft monitored Jupiter's
atmosphere and observed the planet's major satellites. Galileo's mission was
extended in 1997 and again in 1999. Eventually, however, the craft ran low on
fuel. In September 2003, mission managers intentionally crashed Galileo into
Jupiter's atmosphere to avoid any risk of the craft crashing into and
contaminating Jupiter's moon Europa. Galileo's observations of Europa had shown
that it might have an ocean below its surface capable of supporting life.
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Jupiter:
Facts & Figures
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Average
Distance from the Sun
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Metric:
778,412,020 km
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English:
483,682,810 miles
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Scientific
Notation: 7.7841202 x 108 km (5.20336
A.U.)
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By
Comparison: 5.203 x Earth
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Metric:
740,742,600 km
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English:
460,276,100 miles
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Scientific
Notation: 7.407426 x 108 km (4.952 A.U.)
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By
Comparison: 5.036 x Earth
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Metric:
816,081,400 km
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English:
507,089,500 miles
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Scientific
Notation: 8.160814 x 108 km (5.455 A.U.)
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By
Comparison: 5.366 x Earth
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Metric:
71,492 km
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English:
44,423 miles
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Scientific
Notation: 7.1492 x 104 km
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By
Comparison: 11.209 x Earth
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Metric:
449,197 km
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English:
279,118 miles
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Scientific
Notation: 4.49197 x 105 km
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Metric:
1,425,500,000,000,000 km3
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English:
342,000,000,000,000 mi3
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Scientific
Notation: 1.4255 x 1015 km3
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Comparison: 1316 x Earth
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Metric:
1,898,700,000,000,000,000,000,000,000 kg
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Scientific
Notation: 1.8987 x 1027 kg
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Comparison: 317.82 x Earth
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Metric:
1.33 g/cm3
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Comparison: 0.241 x Earth
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Metric:
62,179,600,000 km2
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English:
24,007,700,000 square miles
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Scientific
Notation: 6.21796 x 1010 km2
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Comparison: 121.9 x Earth
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Equatorial
Surface Gravity
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Metric:
20.87 m/s2
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English:
68.48 ft/s2
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Comparison: If you weigh 100 pounds on Earth, you
would weigh 214 pounds on Jupiter.
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Metric:
214,300 km/h
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English:
133,200 mph
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Scientific
Notation: 59,540 m/s
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Comparison: 5.33 x Earth
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Sidereal
Rotation Period (Length of Day)
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0.41354
Earth days
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9.925
hours
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Comparison: 0.4147 x Earth
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Sidereal
Orbit Period (Length of Year)
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11.8565
Earth years
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4330.6
Earth days
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Metric:
47,051 km/h
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English:
29,236 mph
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Scientific
Notation: 13,069.7 m/s
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By
Comparison: 0.439 x Earth
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.04839
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Comparison: 2.90 x Earth
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Orbital
Inclination to Ecliptic
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Equatorial
Inclination to Orbit
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3.12
degrees
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Comparison: 0.0178 x Earth
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Metric:
4,774,000,000 km
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English:
2,996,000,000 miles
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Scientific
Notation: 4.774 x 109 km
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Comparison: 5.165 x Earth
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Metric:
-148 °C
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English:
-234 °F
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Scientific
Notation: 125 K
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Hydrogen,
Helium
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Scientific
Notation: H2, He
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Additional
Information:
Namesake:
King of the Roman gods
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Jupiter/Earth
Comparison
Bulk parameters
Jupiter Earth Ratio (Jupiter/Earth)
Mass (1024 kg) 1,898.6 5.9736 317.83
Volume (1010 km3) 143,128 108.321 1321.33
Radius (1 bar level) (km)
Equatorial 71,492 6,378.1 11.209
Polar 66,854 6,356.8 10.517
Volumetric mean radius (km) 69,911 6,371.0 10.973
Ellipticity 0.06487 0.00335 19.36
Mean density (kg/m3) 1,326 5,515 0.240
Gravity (eq., 1 bar) (m/s2) 24.79 9.80 2.530
Acceleration (eq., 1 bar) (m/s2) 23.12 9.78 2.364
Escape velocity (km/s) 59.5 11.19 5.32
GM (x 106 km3/s2) 126.686 0.3986 317.8
Bond albedo 0.343 0.306 1.12
Visual geometric albedo 0.52 0.367 1.42
Visual magnitude V(1,0) -9.40 -3.86 -
Solar irradiance (W/m2) 50.50 1367.6 0.037
Black-body temperature (K) 110.0 254.3 0.433
Moment of inertia (I/MR2) 0.254 0.3308 0.768
J2 (x 10-6) 14,736 1082.63 13.611
Number of natural satellites 63 1
Planetary ring system Yes No
Orbital parameters
Jupiter Earth Ratio (Jupiter/Earth)
Semimajor axis (106 km) 778.57 149.60 5.204
Sidereal orbit period (days) 4,332.589 365.256 11.862
Tropical orbit period (days) 4,330.595 365.242 11.857
Perihelion (106 km) 740.52 147.09 5.034
Aphelion (106 km) 816.62 152.10 5.369
Synodic period (days) 398.88 - -
Mean orbital velocity (km/s) 13.07 29.78 0.439
Max. orbital velocity (km/s) 13.72 30.29 0.453
Min. orbital velocity (km/s) 12.44 29.29 0.425
Orbit inclination (deg) 1.304 0.000 -
Orbit eccentricity 0.0489 0.0167 2.928
Sidereal rotation period (hours) 9.9250* 23.9345 0.415
Length of day (hrs) 9.9259 24.0000 0.414
Obliquity to orbit (deg) 3.13 23.45 0.133
* System III (1965.0) coordinates
Jupiter Observational Parameters
Discoverer: Unknown
Discovery Date: Prehistoric
Distance from Earth
Minimum (106 km) 588.5
Maximum (106 km) 968.1
Apparent diameter from Earth
Maximum (seconds of arc) 50.1
Minimum (seconds of arc) 29.8
Mean values at opposition from Earth
Distance from Earth (106 km) 628.76
Apparent diameter (seconds of arc) 46.9
Apparent visual magnitude -2.7
Maximum apparent visual magnitude -2.94
Jupiter Mean Orbital Elements
(J2000)
Semimajor axis (AU) 5.20336301
Orbital eccentricity 0.04839266
Orbital inclination (deg) 1.30530
Longitude of ascending node (deg) 100.55615
Longitude of perihelion (deg) 14.75385
Mean Longitude (deg) 34.40438
North Pole of Rotation
Right Ascension: 268.05 - 0.009T
Declination : 64.49 + 0.003T
Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0)
T = Julian centuries from reference date
Jovian Magnetosphere
Goddard Space Flight Center O4 Model
Dipole field strength: 4.28 gauss-Rj3
Dipole tilt to rotational axis: 9.6 degrees
Longitude of tilt: 201.7 degrees
Dipole offset (planet center to dipole center) distance: 0.131 Rj
Latitude/Longitude of offset vector: -8.0 degrees/148.57 degrees
Note:
All latitudes/longitudes are given in Jovian System III (1965.0) coordinates.
Rj denotes Jovian radii, 71,398 km
Jovian Atmosphere
Surface Pressure: >>1000 bars
Temperature at 1 bar: 165 K (-108 C)
Temperature at 0.1 bar: 112 K (-161 C)
Density at 1 bar: 0.16 kg/m3
Wind speeds
Up to 150 m/s (<30 degrees latitude)
Up to 40 m/s (>30 degrees latitude)
Scale height: 27 km
Mean molecular weight: 2.22 g/mole
Atmospheric composition (by volume, uncertainty in parentheses)
Major: Molecular hydrogen (H2) - 89.8% (2.0%); Helium (He) - 10.2% (2.0%)
Minor (ppm): Methane (CH4) - 3000 (1000); Ammonia (NH3) - 260 (40);
Hydrogen Deuteride (HD) - 28 (10); Ethane (C2H6) - 5.8 (1.5);
Water (H2O) - 4 (varies with pressure)
Aerosols: Ammonia ice, water ice, ammonia hydrosulfide
Credit:NASA,Peter J. Gierasch,
Ph.D., Professor of Astronomy, Cornell University. Philip D. Nicholson, Ph.D.,
Professor of Astronomy, Cornell University
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