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Jump
to: Intro, Discovering
Jupiter, Significant
Dates, Page 2: Atmosphere,
Clouds, Interior,
Page 3: Energy, The
Magnetic Field.
INTRO:
Jupiter is the largest of all the planets
in the solar system, 318 times more massive than Earth. Even though it
is of such a great mass, its density is less than twenty five percent of
that of the Earth. These facts indicate that the chemical composition of
this planet is similar to that of the sun, in which it consists mostly
of hydrogen and helium. Jupiter's clouds have one lasting feature, the
great red spot. This is caused by a spinning cloud that is large enough
to encase an area as large as several earths. Jupiter was named after
the king of the Roman gods, the lord of the sky. Jupiter revolves around
the sun with a radius that is five times that of the earth. Due to this,
it can be seen from our skies for most of the year. Each year it appears
to shift about 30 degrees eastward which helps create a 12 year cycle.
Jupiter has no solid surface which leaves nothing to tie down its atmosphere. Thus, Jupiter exhibits differential rotation, meaning that
its rotation rate is not the same from one location to another. Its
equatorial zones rotate more rapidly than the polar regions. The central
temperature of Jupiter is about 20,000 degrees Kelvin, compared to 7000
degrees for earth and 15,000,000 degrees for the sun.
Left: Infared image of Jupiter, taken by
Dr. Richard J. Terrile on Jan. 10, 1979, with the 200 inch Hale
telescope at Palomar Mountain, California, using an infrared detector.
Right: Visible pictures of Jupiter was taken by the Voyager 1 on Jan.
10, 1979.
The coloration of Jupiter is a
result of the interaction of sunlight to the atmosphere and the clouds.
Different chemicals absorb different colors of light. Jupiter has two
distinct features. One is the constantly changing atmospheric bands
arranged parallel to the equator, and the other called the Great Red
Spot. The cloud bands are visible in many different colors: yellows,
blues, browns and reds. Scientists believe that chemical compounds in
Jupiter's atmosphere create these different colors, but the chemistry is
still not completely understood. The Great Red Spot is one of many
features associated with Jupiter's weather. It seems to be an
Earth-sized hurricane that has persisted for hundreds of years.
top...
A remarkable finding of the 1979
Voyager mission was the discovery of a faint ring of matter encircling
Jupiter at its equator. This ring lies roughly 31,000 miles (50,000 km)
above the top cloud layer of this planet and inside the orbit of the
innermost moon. The outer edge of the ring is sharply defined, but only
a few tens of kilometers thick. The dark particles that make up the ring
may have been chipped off by meteorite impacts on two small moons that
lie very close to the ring itself.
Not only is Jupiter the largest planet, it
has four of the largest moons or satellites. These are Io, Europa,
Ganymede, and Callisto. These are known as the Galilean satellites,
after their discoverer, Galileo Galilei in 1610.
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Discovering
Jupiter:
A Pioneer Mission to Jupiter was approved in
1969 by NASA. The goal was to fly two spacecraft by Jupiter, but soon it
was seen that Saturn could be observed as well. Pioneer 10 was launched
on March 2, 1972, and Pioneer 11 on April 3, 1973. These spacecraft
swept across targeted areas but the instruments could not stay in one
single place for a time exposure of any region because of their fixed
rates of rotation. Images were obtained with a scanning photometer. This
was able to be placed perpendicular to the spinning spacecraft. 23
images were transmitted to Earth by Pioneer 10 and 17 by Pioneer 11 in
24 hours. Although the images revealed little new information, new facts
about temperature and pressure within the atmosphere was obtained by
infrared detectors. Astronomers learned of the rich hydrogen atmosphere
similar to our sun.
In 1972, a Voyager mission was created
to observe Jupiter and Saturn. It then included Uranus and Neptune. The
Voyager 1 observed a faint ring around Jupiter's equator. The Voyager 2
sent back views on Jupiter's satellites as well as Jupiter, the planet.
top...
Significant Dates
1610 -- Italian astronomer Galileo Galilei discovered four moons
orbiting Jupiter (Io, Europa, Ganymede, and Callisto-the Galilean
Satellites).
1973 -- Pioneer 10 passed within 130,354 km of Jupiter (12/3/73); cloud tops
and moons imaged.
1974 -- Pioneer 11 passed within 43,000 km of Jupiter (12/2/74)
providing the first images of polar regions.
1979 -- Voyager 1 passed within 350,000 km of Jupiter (3/79) and
discovered a faint ring and three moons.
1979 -- Voyager 2 passed within 650,000 km of Jupiter (7/79) providing
detailed imagery of Jovian ring and Io volcanism.
1989 -- Galileo spacecraft launched (10/18/89).
1995 -- Galileo arrives at Jupiter (12/9/95); atmospheric entry probe
survives to pressure depth of 23 bars.
1999 -- Galileo orbits in Jupiter's system, studying planet, rings,
satellites, and magnetosphere.
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