Everything about Jupiter totally explained
Jupiter (pronounced ) is the fifth
planet from the
Sun and the
largest planet within the
Solar System. It is two and a half times as massive as all of the other planets in our Solar System combined. Jupiter, along with
Saturn,
Uranus and
Neptune, is classified as a
gas giant. Together, these four planets are sometimes referred to as the
Jovian planets, where
Jovian is the
adjectival form of Jupiter.
The planet was known by
astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. The
Romans named the planet after the
Roman god Jupiter. Through
infrared and
ultraviolet measurements, trace amounts of
benzene and other
hydrocarbons have also been found.
The atmospheric proportions of hydrogen and helium are very close to the theoretical composition of the primordial
solar nebula. However, neon in the upper atmosphere only consists of 20 parts per million by mass, which is about a tenth as abundant as in the Sun. Helium is also depleted, although to a lesser degree. This depletion may be a result of precipitation of these elements into the interior of the planet. Abundances of heavier inert gases in Jupiter's atmosphere are about two to three times that of the sun.
Based on
spectroscopy,
Saturn is thought to be similar in composition to Jupiter, but the other gas giants
Uranus and
Neptune have relatively much less hydrogen and helium. However, because of the lack of atmospheric entry probes, high quality abundance numbers of the heavier elements are lacking for the outer planets beyond Jupiter.
Mass
Jupiter is 2.5 times more
massive than all the other planets in our Solar System combined—this is so massive that its
barycenter with the Sun actually lies above the Sun's surface (1.068
solar radii from the Sun's center). Although this planet dwarfs the Earth (with a diameter 11 times as great) it's considerably less dense. Jupiter's volume is equal to 1,317 Earths, yet is only 318 times as massive.
Theoretical models indicate that if Jupiter had much more mass than it does at present, the planet would shrink. For small changes in mass, the radius wouldn't change appreciably, and above about four Jupiter masses the interior would become so much more compressed under the increased gravitation force that the planet's volume would actually
decrease despite the increasing amount of matter. As a result, Jupiter is thought to have about as large a diameter as a planet of its composition and evolutionary history can achieve. The process of further shrinkage with increasing mass would continue until appreciable
stellar ignition is achieved as in high-mass
brown dwarfs around 50 Jupiter masses. This has led some astronomers to term it a "failed star", although it's unclear whether or not the processes involved in the formation of planets like Jupiter are similar to the processes involved in the formation of multiple star systems.
Although Jupiter would need to be about seventy-five times as massive to fuse hydrogen and become a
star, the smallest
red dwarf is only about 30% larger in radius than Jupiter. In spite of this, Jupiter still radiates more heat than it receives from the Sun. The amount of heat produced inside the planet is nearly equal to the total solar radiation it receives. This additional heat radiation is generated by the
Kelvin-Helmholtz mechanism through
adiabatic contraction. This process results in the planet shrinking by about 2 cm each year. When it was first formed, Jupiter was much hotter and was about twice its current diameter.
Internal structure
Jupiter is thought to consist of a dense
core with a mixture of elements, a surrounding layer of liquid
metallic hydrogen with some helium, and an outer layer predominantly of
molecular hydrogen.
Above the layer of metallic hydrogen lies a transparent interior atmosphere of
liquid hydrogen and
gaseous hydrogen, with the gaseous portion extending downward from the cloud layer to a depth of about 1,000 km.
This smooth transition happens whenever the temperature is above the
critical temperature, which for hydrogen is only 33
K (see
hydrogen).
The temperature and pressure inside Jupiter increase steadily toward the core. At the
phase transition region where liquid hydrogen (heated beyond its critical point) becomes metallic, it's believed the temperature is 10,000 K and the pressure is 200
GPa. The temperature at the core boundary is estimated to be 36,000 K and the interior pressure is roughly 3,000–4,500 GPa. The zones have been observed to vary in width, color and intensity from year to year, but they've remained sufficiently stable for astronomers to give them identifying designations. The water clouds can form thunderstorms driven by the heat rising from the interior.
The orange and brown coloration in the clouds of Jupiter are caused by upwelling compounds that change color when they're exposed to
ultraviolet light from the Sun. The exact makeup remains uncertain, but the substances are believed to be phosphorus, sulfur or possibly hydrocarbons. and possibly since 1665.
Mathematical models suggest that the storm is stable and may be a permanent feature of the planet. The storm is large enough to be visible through Earth-based
telescopes.
The
oval object
rotates counterclockwise, with a
period of about 6 days. The Great Red Spot's
dimensions are 24–40,000 km × 12–14,000 km. It is large enough to contain two or three planets of Earth's diameter. The maximum altitude of this storm is about 8 km above the surrounding cloudtops.
Storms such as this are common within the
turbulent atmospheres of
gas giants. 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 for hours or
centuries.
Even before Voyager proved that the feature was a storm, there was strong evidence that the spot couldn't be associated with any deeper feature on the planet's surface, as the Spot rotates differentially with respect to the rest of the atmosphere, sometimes faster and sometimes more slowly. During its recorded history it has traveled several times around the planet relative to any possible fixed rotational marker below it.
In 2000, an atmospheric feature formed in the southern hemisphere that's similar in appearance to the Great Red Spot, but smaller in size. This was created when several smaller, white oval-shaped storms merged to form a single feature—these three smaller white ovals were first observed in 1938. The merged feature was named
Oval BA, and has been nicknamed Red Spot Junior. It has since increased in intensity and changed color from white to red.
Planetary rings
Jupiter has a faint
planetary ring system composed of three main segments: an inner
torus of particles known as the halo, a relatively bright main ring, and an outer "gossamer" ring. These rings appear to be made of dust, rather than ice as is the case for Saturn's rings. In a similar way, the moons
Thebe and
Amalthea probably produce the two distinct components of the gossamer ring.
At about 75 Jupiter radii from the planet, the interaction of the magnetosphere with the
solar wind generates a
bow shock. Surrounding Jupiter's magnetosphere is a
magnetopause, located at the inner edge of a
magnetosheath, where the planet's magnetic field becomes weak and disorganized. The solar wind interacts with these regions, elongating the magnetosphere on Jupiter's
lee side and extending it outward until it nearly reaches the orbit of Saturn. The four largest moons of Jupiter all orbit within the magnetosphere, which protects them from the solar wind.
Orbit and rotation
The average distance between Jupiter and the Sun is 778 million km (about 5.2 times the average distance from the Earth to the Sun, or 5.2 AU) and it completes an orbit every 11.86 years. The elliptical orbit of Jupiter is inclined 1.31° compared to the Earth. Because of an
eccentricity of 0.048, the distance from Jupiter and the
Sun varies by 75 million km between
perihelion and
aphelion, or the nearest and most distant points of the planet along the orbital path respectively.
The axial tilt of Jupiter is relatively small: only 3.13°. As a result this planet doesn't experience significant
seasonal changes, in contrast to Earth and Mars for example.
Jupiter's
rotation is the fastest of all the Solar System's planets, completing a rotation on its
axis in slightly less than ten hours; this creates an
equatorial bulge easily seen through an Earth-based amateur
telescope. This rotation requires a
centripetal acceleration at the equator of about 1.67 m/s², compared to the equatorial surface gravity of 24.79 m/s²; thus the net acceleration felt at the equatorial surface is only about 23.12 m/s². The planet is shaped as an
oblate spheroid, meaning that the
diameter across its
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.
Observation
Jupiter is usually the fourth brightest object in the sky (after the Sun, the
Moon and
Venus);
Earth overtakes Jupiter every 398.9 days as it orbits the Sun, a duration called the
synodic period. As it does so, Jupiter appears to undergo
retrograde motion with respect to the background stars. That is, for a period of time Jupiter seems to move backward in the night sky, performing a looping motion.
Jupiter's 12-year orbital period corresponds to the dozen
constellations in the
zodiac.
Research and exploration
Ground-based telescope research
In 1610,
Galileo Galilei discovered the four largest
moons of Jupiter,
Io,
Europa,
Ganymede and
Callisto (now known as the
Galilean moons) using a telescope; thought to be the first observation of moons other than Earth's. Note, however, that Chinese historian of astronomy, Xi Zezong, has claimed that
Gan De, a Chinese astronomer, made this discovery of one of Jupiter's moons in
362 BC with the unaided eye, nearly 2 millennia earlier. Galileo's was also the first discovery of a
celestial motion not apparently centered on the Earth. It was a major point in favor of
Copernicus' heliocentric theory of the motions of the planets; Galileo's outspoken support of the Copernican theory placed him under the threat of the
Inquisition.
During 1660s, Cassini used a new telescope to discover spots and colorful bands on Jupiter and observed that the planet appeared oblate; that is, flattened at the poles. He was also able to estimate the rotation period of the planet. In 1690 Cassini noticed that the atmosphere undergoes
differential rotation.
The Red Spot was reportedly lost from sight on several occasions between 1665 and 1708 before becoming quite conspicuous in 1878. It was recorded as fading again in 1883 and at the start of the twentieth century.
Both
Giovanni Borelli and Cassini made careful tables of the motions of the Jovian moons, allowing predictions of the times when the moons would pass before or behind the planet. By the 1670s, however, it was observed that when Jupiter was on the opposite side of the Sun from the Earth, these events would occur about 17 minutes later than expected.
Ole Rømer deduced that sight isn't instantaneous (a finding that Cassini had earlier rejected
In 1892,
E. E. Barnard observed a fifth satellite of Jupiter with the 36-inch refractor at
Lick Observatory in California. The discovery of this relatively small object, a testament to his keen eyesight, quickly made him famous. The moon was later named
Amalthea. It was the last planetary moon to be discovered directly by visual observation. An additional eight satellites were subsequently discovered prior to the flyby of the
Voyager 1 probe in 1979.
In 1932,
Rupert Wildt identified absorption bands of ammonia and methane in the spectra of Jupiter.
Three long-lived anticyclonic features termed white ovals were observed in 1938. For several decades they remained as separate features in the atmosphere, sometimes approaching each other but never merging. Finally, two of the ovals merged in 1998, then absorbed the third in 2000, becoming
Oval BA.
In 1955, Bernard Burke and
Kenneth Franklin detected bursts of radio signals coming from Jupiter at 22.2 MHz.
Scientists discovered that there were three forms of radio signals being transmitted from Jupiter.
