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About Jupiter Date Published: by Clarke Fountain
Bio: Clarke Fountain

Clarke Fountain has been studying astrology with varying levels of intensity since the 1960s, is a U.S. Navy veteran, and gave his first professional reading in 1977 in San Francisco. After years of doing every kind of job under the sun, he earned an M.A. in Buddhist Studies from the Naropa Institute (as it was then called) in 1989 and at that time became involved with aspects of publishing. Astrology has been one of the few consistent threads in his otherwise extremely varied life, and he is delighted to have the opportunity to serve the astrological community as the Editor for "Astro Talk Online Astrological Magazine."



This little data festival is an appropriate way to honor the passage of Jupiter through Gemini. The astrological properties of the King of Planets are such that mere data is somewhat repugnant to it. However, when it is plunged into the data swamps of Gemini, it must cope with this dry stuff. Usually it prefers to deal with information in terms of its place in the great picture, the grand perspective, the meaning of things. Those of you with a passion for raw information, however, will, the editors hope, have a field day with the material in this article.

Physical Characteristics

It is appropriate that the planet named after the king of the gods should be the largest by far in our solar system. If the matter from every other planet (with satellites) was clumped together into one huge heap, that would still be only half that needed in order to make one Jupiter.

It may surprise some who either never learned this in high-school chemistry or have long forgotten it, but the element hydrogen is of the same basic strain as the metallic elements. Jupiter contains an enormous amount of pure hydrogen, both in liquid form, and in something called "fluid metallic" form. The kind of mercury we used to get in thermometers is a possible analogy to help readers understand this state of matter. Molten lead is yet another. However, it is believed that all that liquid metallic hydrogen is responsible for generating the second-largest magnetic field in the solar system (the sun has the largest magnetic field). The flow of charged particles within that field, which includes several of Jupiter's closest satellites, is responsible for many of the odd physical properties they exhibit. The radiation from the charged particles trapped in Jupiter's magetosphere is sufficiently intense to kill an unprotected human instantly.

The second most plentiful element in Jupiter's makeup is helium. In that respect it is quite similar to the sun. Indeed, some have considered that it is a failed "twin" to the sun that failed to ignite. If so, it would need considerably more mass than it currently has to begin nuclear fusion.

It is believed to have a rocky core with many times the earth's mass, and has a "regular" gas giant planet atmosphere composed mostly of ammonia. Given the tremendous speed at which the huge planet rotates, centrifugal force roils the atmosphere in gigantic storms, like the "Great Red Spot" amateur astronomers are able to see on its surface so easily. Winds move at speeds in excess of 400 miles per hour. In addition, its swift rotation (approximately once every ten Earth hours) gives the planet an oddly flattened appearance, as it is much wider at the equator than at the poles.

Jupiter puts out twice the energy that it receives from the sun.

Jupiter puts out twice the energy that it receives from the sun. Scientist now think that most of this heat comes from the gravitational pressure its huge mass exerts on the material it is composed of.

Jupiter has been studied by science packages in space, beginning with Pioneer 10 in 1973 and culminating in the current Galileo fly-by. Other spacecraft to contribute to our knowledge of this vast planet are Ulysses, Voyagers 1 and 2, and Pioneer 11. The Galileo spacecraft sent a probe into the upper layers of Jupiter's atmosphere, and though it perished after getting only about 150 kilometers into it, a great deal of information resulted.

Like Saturn, Jupiter has been found to have rings. However, the matter composed of them has a very low reflectivity (albedo) and their existence was only discovered recently.

Of the 16 known satellites of Jupiter, one (Europa) is believed capable of sustaining life, albeit in a very strange form. Ganymede, with a diameter of 3,268 mi/5,262 km is larger than the planet Mercury; all four of the largest satellites are larger than Pluto (1,419 miles). Of the three other quite large satellites, two of them are larger than the Earth's moon. Callisto (3,000 mi/4,806 km) and Io (2,255 mi/3,630 km) both beat out the moon (2,160 mi), while Europa (1,960 mi/3,130 km) comes awfully close.

Io has active volcanos spewing sulfur plumes into space, as observed by visiting spacecraft from earth, and Europa shows considerable evidence of current tectonic (earthquake) activity in its icy crust.

Symbolic Jupiter

In Western Astrology Jupiter has long been given rulership over the sign of Sagittarius, and is the ancient ruler of the sign Pisces, which many now believe is ruled by Neptune. Adjectives applied to the planet, based at least in part on its connection to the Graeco-Roman deities it is associated with, include "the greater benefic," "the planet of luck," and "lifepath," among others. Anciently, the planet is given rulership over growth, the law and the principles of government, formal religion, with the medicine of healing, and "higher" education of all kinds. Afflicted, it can present possibilities of arrogance, weight gain, and unrealistic optimism.

In Vedic Astrology

Vedic astrology assigns the quality of "sattvic" (pure) to Jupiter, and give it the element of "ether," a fifth element in addition to the traditional four of earth, air, fire and water. It is called the planet of "dharma" (law of our inner path) and governs wealth; another name for the planet is "guru" (spiritual teacher), and it governs creativity, high principles, and other good things such as intelligence (as opposed to simply the intellect). It is the planet whose astrological condition reflects the avenues and ways we find much that brings joy in our lives, including creative activity and children. Afflicted, it can represent over-optimism and a materialistic attachment to wealth. Priesthood and formal religion, insofar as they enrich our lives and expand our spirits, are also under this planet's Vedic rulership.

Symbolic Associations

In the Mediterranean mythologies, the Roman sky-god Jupiter (also called Jove) was also associated with the Greek gods Zeus and Iacchus, and with the Babylonian Marduk. Egyptian attributions are hazier, but Amon, Isis, Amon-Ra and Nu have been suggested. Symbols connected to the planet and mythological deity include the eagle (a very strong association); olive, aspen, cedar, oak, poplar and fig trees; the semiprecious stones amethyst, chalcedony, topaz, and lapis lazuli; and so on (A. Crowley: "Liber 777"). Numerologically, Jupiter has been associated with the number 4, and all numbered tarot cards bearing that number, as well as the trumps "The Fool" and "The Wheel of Fortune." It is also assigned to the (fourth) sphere on the Tree of Life, Chesed, the middle position on the Pillar of Mercy.


As a deity Jupiter had a roving eye, much to the disgust of his wife Juno, and his liaisons included female (and male) beauties of the human and animal realms. The four largest satellites of the planet Jupiter are named after some of his conquests (Callisto, Io, Ganymede and Europa) - as are the majority of the planet's other 12 satellites. A very amorous being, indeed! Many mythological stories from ancient Rome feature his romantic adventures (and Juno's attempts to get revenge on him for them). Like many other deities of ancient myth, he is reputed to have occasionally put on a human disguise and gone about on the earth, spying on (and occasionally intervening in) the affairs of men.

In Roman Life

Jupiter was "the king of the gods" for the Romans, and his cult remained central to the continuity of the state in his guise as "Juppiter Optimus Maximus" (best and greatest of Jupiters). Even the cult of the Emperor-as-god never displaced Jupiter from primacy. His sacred sites were hills and any place struck by lightening. Lightening strikes were often fenced off as holy places, dedictated to Jupiter. Like other Graeco-Roman deities, his was not a single cult, but had many variations. Among these are Jupiter Elicius, Jupiter Fulgur and Jupiter Latiaris. Jupiter was greatly associated with the sacredness of oaths, hence the still-common use in English of the expression "by Jove." The ways in which aspects of Jupiter were involved in Roman life are too numerous to list here, but practically nothing of great importance happened in Roman life without some ceremony to Jupiter taking place.

Astronomical Data Tables for Jupiter

Mean radius69,911 km
Diameter (equatorial)88,815 mi (142,984 km)
Mass317.8 (Earth = 1) or 1.900e27 kg
Density1.31 (g/cm^3)
Gravity2.34 (Earth = 1)
Orbital Period11.86 Earth years
Rotation Period.414 Earth Days (9 hours 55 min.)
Semimajor axis of orbit 5.2 au (astronomic units)
Eccentricity of orbit0.004 (not very eccentric)
Distance from the Sun483.6 million miles (778.3 million km)
Temperature at surface-190F (-124C)
Temperature at planet core (estimated)25,000 K



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Fountain, ClarkeInterview with Steven Forrest and Jeffrey Wolf Green



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