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Venus, in astronomy
Venus, in astronomy, 2d planet from the sun; it is often called the evening star or morning star and is brighter than any object in the sky except the sun and the moon. Because its orbit lies between the sun and the orbit of the earth, Venus passes through phases like those of the moon, varying from a large bright crescent when the planet is near inferior conjunction (nearest the earth) to a smaller silvery disk when it is at superior conjunction (farthest from the earth). Since its greatest elongation (the angle made between the sun, the earth, and Venus) is 47°, it can never be seen much longer than 3 hr after sunset or 3 hr before sunrise.
Venus revolves around the sun at a mean distance of c.67 million mi (107 million km) in a nearly circular orbit, and its period of revolution is about 225 days. It comes closer to the earth than any other planet, being c.26 million mi (42 million km) away at inferior conjunction. Venus is often referred to as the sister planet of the earth, because it is only slightly smaller in both size and mass. Several important differences, however, exist between the two planets.
Although Venus is covered with a thick blanket of clouds that hides its surface from view, much has been learned of the conditions on Venus from U.S. and Soviet space probes. These probes indicate a surface temperature of about 890℉ (475℃) and an atmospheric pressure as great as 100 times that at the earth's surface. The thick atmosphere is composed mainly of carbon dioxide, with a slight amount of water vapor and a trace of nitrogen and other elements. The high surface temperature is assumed to result partly from the greenhouse effect; radiation passing through the atmosphere heats the surface, but the heat is blocked by the enveloping carbon dioxide from escaping back out through the atmosphere. The European Space Agency's Venus Express space probe began orbiting the planet in 2006; its instruments are designed primarily to study the Venusian atmosphere.
Studies also indicate that Venus rotates on its axis in a retrograde direction (opposite to the direction of revolution about the sun) with a period of about 243 days. Despite this slow rotation there is little observed temperature difference between the lighted and unlighted sides of the planet. The surface of Venus is thought to be stormy.
From 1990 to 1992 NASA's Magellan spacecraft mapped the Venusian surface using radar, revealing details of a continentlike feature, called Aphrodite Terra, that crosses the planet's equator and is marked by geologic faults. A second such feature, Ishtar Terra, straddles the north polar region. Magellan also observed many volcanic features, including immense lava plains and large shield volcanoes, and relatively few impact craters resulting from asteroids and comets. Compared to the number of craters on other bodies of the inner solar system, this suggests that the surface of Venus is only about 800 million years old. No strong magnetic field comparable to that of the earth has been detected.
Venus, in Roman religion and mythology
Venus(vee -nŭs) The second planet of the Solar System in outward succession from the Sun and the one that comes closest to the Earth. It orbits the Sun every 224.7 days at a distance varying between 0.72 and 0.73 AU. It has a size (12 104 km equatorial diameter), density, and, probably, internal constitution comparable with those of the Earth, but measurements by Mariner, Pioneer Venus, Venera, Vega, Magellan, and Galileo spaceprobes have revealed extremely hostile surface and atmospheric conditions. Orbital and physical characteristics are given in Table 1, backmatter.
Venus is never far from the Sun in the sky, reaching its greatest elongation of 45° to 47° about 72 days before and after inferior conjunctions, which recur at intervals of about 584 days. At greatest brilliancy the planet is near magnitude –4.4 and brighter than every other celestial object except the Sun and the Moon; this occurs at an elongation of 39° about 36 days before and after inferior conjunction, while Venus is an evening star or a morning star.
Telescopically the planet shows a brilliant yellowish-white cloud-covered disk. Because of its orbital position between Sun and Earth, Venus exhibits phases: gibbous and crescent phases occur between full at superior conjunction, when the planet's apparent diameter is 10 arc seconds, and new at inferior conjunction, when it has a diameter of about 61 arc seconds. Transits of Venus across the Sun's disk at inferior conjunction are rare and currently come in pairs: the next will occur in 2012 – this will be the second of a pair, the first having taken place in 2004. After 2012, there will not be another until 2117.
The clouds never permit views of the surface of Venus; it was not until 1961 that radar established that Venus rotated in a retrograde direction 243.01 days relative to the stars, or 116.8 days in relation to the Sun (the Venusian day). Features in the clouds, seen indistinctly from the Earth but observed in detail by ultraviolet photography from Pioneer Venus and Mariner 10, indicate a four-day east to west rotation period for the upper atmosphere, corresponding to 350 km/hour winds. The atmosphere thus rotates in the same direction but about 60 times faster than the solid planet. The cloud patterns swirl from the equator toward the poles and appear to be driven by solar heating and convection near the subsolar point in the middle of the sunlit hemisphere.
Possibly because of the slow rotation of its nickel-iron core, Venus has little or no intrinsic magnetic field. A magnetic field is however induced in the planet's ionosphere by the solar wind. The resulting bow shock wave was found by one of the Pioneer Venus probes to be very strong and can therefore buffer the outer atmosphere of Venus from the solar wind.
The atmosphere extends to about 250 km above the surface. Pioneer Venus measurements showed there to be a layered structure to the Venusian clouds, which lie between altitudes of roughly 45–60 km within the troposphere of Venus (i.e. the region in which the atmospheric temperature decreases with altitude). There is haze above and below the clouds. Three cloud layers have been distinguished, having different concentrations and sizes of suspended particles; the particles are identified as liquid droplets of sulfuric acid with an admixture of water and solid and liquid particles of sulfur.
The temperature increases from about 300 K at the cloud tops to about 730 K at Venus' surface, which experiences a crushing atmospheric pressure 90 times that of the Earth. The surface temperature, higher than that of any other planet, is the result of a greenhouse effect involving the clouds and the large proportion of carbon dioxide in the atmosphere. Pioneer Venus showed that the atmosphere as a whole consists of about 98% carbon dioxide, 1–3% nitrogen, with a few parts per million (ppm) of helium, neon, krypton, and argon. Although the amounts of neon, krypton, and argon are small, they indicate very much greater amounts of primordial neon, krypton, and argon than those found in the Earth's atmosphere. This is currently raising problems concerning the established view of the origin of the Solar System. In the lower atmosphere, below the clouds, trace amounts of water vapor (0.1–0.4%) and free oxygen (60 ppm) were detected. The high surface temperature may have prevented any atmospheric water vapor from condensing into oceans, as occurred on Earth; it may also have prevented carbon dioxide from combining with the crustal material to form carbonaceous rocks. The upper atmospheric winds moderate to only 10 km/hour or so at the surface.
Photographs of the surface returned by the Venera 9 and 10 landers in 1975 showed a stony desert landscape, while tests for radioactive elements in the crust implied a composition similar to that of basalt or granite. Radar mapping of the surface of Venus was done by the Pioneer Venus, Venera 15 and 16, and Magellan spacecraft. Magellan mapped 98% of the surface, obtaining a resolution of 100 meters in places.
Huge rolling plains cover 65% of the surface, depressions cover 27%, and highland areas cover the remaining 8%, concentrated in two main areas – Ishtar Terra and Aphrodite Terra. Ishtar Terra, the more northerly, is a flattish plateau bounded on three sides by mountains. Maxwell Montes, one of these mountainous regions, is the highest range on Venus, rising to more than 11 km above the mean elevation of the surface.
Almost everywhere, the surface of Venus displays evidence of volcanism. The larger shield volcanoes are generally located on top of the broad highland areas, while small volcanoes of only a few km across appear to exist over all the surface. Scores of small volcanic domes, all less than 15 km across, pepper the southern flank of the highland area Tethus Regio. The Eistla region has circular volcanic domes (‘pancake’ domes), some up to 65 km in diameter, with broad flat tops less than 1 km in height. These are formed from viscous lava.
Magellan observed more than 900 craters on Venus. The planet does not have impact craters less than a few km across because its thick atmosphere causes smaller objects to disintegrate totally before they reach the surface. Many craters are surrounded by huge radar-dark halos, the result of a shock wave that built up ahead of the object in Venus' atmosphere and pulverized the uppermost few meters of rock to produce a smooth blanket of material. The distribution of craters on Venus is statistically uniform and very few are altered by later volcanic activity.
Other features include wind streaks, tesserae, coronae, and deep chasms. Complex lava flows exist; the area of Mylitta Fluctus in Lavinia Planitia covers roughly 800 km by 400 km. Long narrow channels meander for great distances; for example Hildr Fossa extends for 6800 km but is only 1–2 km wide over its entire length with no lakes or tributaries. It may have been formed by extremely fluid lava flowing across a vast flat plain. It is clear that Venus has had an active geological history; no evidence has been found, however, for plate tectonics.
Venus(religion, spiritualism, and occult)
Venus is the second planet from the Sun, located between Mercury and Earth. It is the most notable light in the sky, after the Sun and Moon, and has been referred to as Earth’s sister planet. Nearly the same size as Earth, Venus orbits around the Sun in a nearly circular path of 225 days. Venus also rotates on its axis in the opposite direction of the Earth and most other planets, turning from east to west, and so slowly that one Venus day is the equivalent of 243 Earth days, longer than its year. In so doing Venus only shows one side of itself to the Earth at its closest orbital proximity.
As a planet nearer to the Sun than Earth, Venus is considered an inferior planet and is never seen to be more than 48° of longitude away from the Sun. As Venus moves along its orbit, it appears from Earth’s perspective to periodically slow, stop, and then move backwards. This so-called retrograde motion lasts approximately six weeks, which ends when Venus seems to stop briefly and move forward again. The retrograde motions of Venus happen at regular intervals, taking place five times within the greater eight-year Venus cycle.
It is this eight-year cycle that is recorded on the Venus tablet of Amisaduaq, the tablet of Mesopotamian omens based on the movements of Venus. It dates from approximately 1750 to 1650 b.c.e. and is the earliest known astrological document. In addition, the tablet emphasizes the first and last visibilities of Venus, those times Venus is seen rising just prior to the Sun or setting after it. In the first instance Venus has not been visible for a time, as it has been too close to the sun. Its first visibility is the first morning it can be spotted rising before the Sun, heralding the coming dawn. Similarly, the last visibility is the last time Venus was seen setting on the tail of the Sun. It then disappears for a time behind the Sun’s light. These two distinctly different sightings were important as they recognized the dual nature of Venus.
The Sumerian Inanna was the goddess of love, fertility, desire, and attraction. She presided over the passions, some of which were destructive ones such as jealousy and anger. Inanna also claimed possession of the Tablets of Destiny, giving her control of the universe. She was the most powerful of deities. Sumerian poetry describes her as Queen of Heaven, Lady of the Evening, as well as Lady of Light, associating Inanna with the planet Venus as both the rising and setting star. Her dual nature ruled over both love and hate, light and dark as seen in her mythology, which includes stories of her descent into the underworld as well as her return to the land of living. The ancients equated the disappearance of Venus with her descent into the underworld. There she had to face herself at her most vulnerable, die, and then rise again as Queen of Heaven and Earth.
When the Akkadians settled in Sumerian territory Inanna’s name changed to Ishtar. Babylonian poetic descriptions of the descent of Ishtar are nearly identical to the myths of Inanna with the exception of a more forceful warrior like temperament in Ishtar. Thus Ishtar also had the dual characteristics of love and attraction as the evening star as opposed to lust and hostility as the morning star. This was reflected in Babylonian astrological omens where good or evil outcomes were indicated by Ishtar’s placements.
While the Mesopotamian lands repeatedly changed hands to be led by the Assyrians and then the conquering Persians, the goddess associated with Venus changed names to the Syrian Astarte followed by the Persian Anahita. The goddess continued to be seen as the source of all waters and fertility on the earth, the holder of wisdom and benefactress of the human race. Beautiful, bright and adorned with gold, she was the seductive goddess, symbolizing the tradition of temple prostitution. Astrology centered on the reading of omens also continued in Babylon, however by the sixth century b.c.e. the planets began to be seen as either malefic or benefic, rather than dependent on season or rising time, and Venus became overwhelmingly benefic.
The Greeks received knowledge of astrology and the five wandering stars from the Babylonians. In equating the planets to their own pantheon of gods they equated Ishtar with Aphrodite, their goddess of love and beauty. The fertility aspects of Ishtar were seen in Demeter and her mythological descents into the underworld equated with Demeter’s daughter Persephone. In addition, Athena was the Greek holder of wisdom as well as the patron goddess of righteous warriors, associations formerly held by Inanna/Ishtar. However, the volatile temperament of Ishtar was fully present in the Greek Aphrodite as indicated by myths displaying her jealousy, anger, and possessiveness.
The planet Venus was called the star of Aphrodite in fourth century b.c.e. Greece, recognizing it as the home of the goddess. Sometime during the Hellenic period of Alexandria, the flourishing Greek astrology began referring to the planet as simply Aphrodite. Vettius Valens, who recorded an Anthology of Hellenistic astrology in the second century c.e., wrote that the nature of Aphrodite was desire and erotic love, and that it signified the mother and nurse. The star represented priestly rites, parties, weddings, friendships, jewels and ornaments, music, beauty, the arts, as well as a variety of colors. It gave gifts of businesses, involved markets and weights and measures, bestowed favors from female royals or relatives and assured an excellent reputation. It was lord of the neck, face, and lungs, and ruled sexual intercourse. It also indicated the giving of nurturing or pleasure to another. It was the lord of precious stones and the oil of fruits, its color was white, and it belonged to the nocturnal (lunar) sect, along with Ares (Mars) and Hermes (Mercury, as evening star).
Hellenistic astrology included basic functions of the planets, and if one is to assume that Ptolemy’s record is representative of astrologers for that period, then a relationship was present between the basic qualities of matter and each of the planets. Aphrodite is listed as temperate (slightly warm) and moist, meaning that it has an active power that attracts as well as a passivity that can include others within its boundaries. Its basic nature was unification and reconciliation. In a solar (daytime) chart Aphrodite is out of, or contrary to, sect so the unions it represents do not come together naturally, but through thought and choice. Whereas in a lunar (night) chart Aphrodite is in sect and relational things come together more easily.
Just as in modern day, Aphrodite ruled the zodiac signs of the Bull (Taurus) and the Balance (Libra), and was exalted in the Fishes (Pisces). It had additional rulerships of Trigons, Bounds, and Faces—divisions that for the most part do not exist in astrology today. Aphrodite as a nocturnal planet was a trigon lord only in a night chart where it ruled all of the feminine signs: the Bull, the Crab (Cancer), the Virgin (Virgo), the Scorpion (Scorpio), the Goat-Horned One (Capricorn), and the Fishes. As for rulerships of bounds and faces (or decans), tables can be consulted to determine these, as they require exact degrees of signs to determine.
Astrology was introduced to the Romans by way of imported slaves. They embraced the Hellenistic practice without alteration, except that they renamed Aphrodite for their goddess of fertility, joy, and beauty—Venus. Through their association with the Alexandrian Greeks, the Romans came to view Venus primarily as the goddess of love and the planet Venus as her abode. Eventually the planet would be thought of as Venus herself, a substitution for the goddess, and the name for the second planet remained Venus on into modern day.
Classical astrology of the Middle Ages had some similarities to the Hellenistic, however the associations for Venus show quite a few variations between them, particularly as to the rulership of body parts, but also in a propensity to expand on the negative, underworld significations of Venus. It represented the force of attraction as well as love and beauty and ruled physical beauty, parts of the face, the throat, the female sex organs, and sense of taste. Like Hellenistic Aphrodite, Venus symbolized women, art, music, and relationships, and was fertile and creative. However, it also signified adulterers, flirts, incest, infertility, kidney and venereal disease, prostitutes, and scandal.
The system of essential dignities had Venus ruling Taurus and Libra and exalted in Pisces, a practice that has not changed throughout history. The classic dignities also included tables of Triplicities, Terms, and Faces that varied according to the practice of the astrologer. William Lilly gave the diurnal, or daytime, triplicities of Taurus, Virgo, and Capricorn to Venus; while the Dorothean, or Ptolemaic, tables added the water signs Cancer, Scorpio, and Pisces to that list. Venus had no nocturnal triplicity rulerships. The terms were signs divided into five parts by degree. The terms of Venus are best consulted in those tables. The faces were essentially decans, or 10° increments of signs. Venus was in her own face in the first 10° of Cancer and Aquarius, the second 10° of Virgo, and the third 10° of Aries and Scorpio.
Vedic astrology, or Jyotish, has some similarities to the Hellenistic methods of astrology. Venus rules Taurus and Libra, and is connected to the wife, marriage, women, beauty, art, and music. Venus is called Sukra (Shukra), but is seen as a male god. The deities associated with Venus are Lakshmi, the goddess of love and pleasure, as well as Indra, the thunderbolt warrior god who also represents desires and yearnings. Sukra rules the face, kidneys, and reproductive system and is associated with harmony, flowers, happiness, and pleasure as well as laziness, vanity, and addictions. He represents love and the ability to relate to another. Sukra’s colors are multicolored, his gemstones are diamond and white sapphire, and his day is Friday.
As a benefic, Venus enhances the house in which it is placed as well as providing a good influence on planets associated with it by house or aspect. Sukra (Venus) is a friend to Mercury and Saturn, is an enemy to the Sun and Moon, and neutral with Mars and Jupiter. In the zodiac sign of a friend it is joyful, contented, glad, and rejoicing. In the sign of an enemy it is sleepy, drowsy, and numb. Sukra (Venus), as in western astrology, is exalted in Pisces. Jyotish defines the exact degree of exaltation as 27° of Pisces (sidereal) and similarly the exact degree of debilitation of Venus is 27° of Virgo (sidereal). As it moves toward the exact degree the intensity of its benefic or debilitated state is increased.
Venus also rules three of the 27 Nakshatras (lunar mansions): Bharani (0 to 13°20’ Aries, sidereal), Purva Phalaguni (13°20’ to 26°40’ Leo, sidereal), and Purva Ashadha (13°20’ to 26°40’ Sagittarius, sidereal). All three of these Nakshatras share a sense of passion that requires one to learn restraint.
Today’s western astrology combines many of the historical attributes of Venus. The planet is associated with the Greco/Roman goddess Venus and rules love and marriage as well as harmony and the ability to attract. The modern Venus is quite feminine in nature, represents grace, elegance, and beauty as well as money and material goods. She is the patron of the arts and music, and reflects one’s ability to navigate social situations. Relationships, the capacity for affection, friendships, sensuality, and sexuality all belong under her domain.
The sign that Venus is posited in at birth indicates how one relates to others, what one finds attractive and one’s capacity for love and harmony. The house in which Venus resides, as well as the houses the planet rules, describe the areas of life that are most profoundly impacted. For instance, harmony or money issues may be more important in those areas. In addition, the attractive nature of Venus usually brings a love of, or interest in, those things represented by those houses.
The shadow side of Venus recognizes that overindulgence brings out some negative traits, which can be indicated by retrograde motion, or aspects with another planet, as well as placement in a difficult house, such as the twelfth. For example, Jupiter aligned with Venus may seem to be a lucky placement. However, the expansive nature of Jupiter may influence Venus to overspend and to be vain or lazy.
As in the Hellenistic and Jyotish traditions, Venus rules the zodiac signs of Taurus and Libra, is exalted in Pisces, in detriment in Aries and Scorpio, and in its fall in Virgo. Physically, modern Venus rules the female sex organs, the glands, blood in the veins, the throat, and the kidneys. She is associated with the voice, etiquette, sweets, flowers, perfume, copper, Friday, and the number six.
—Linda R. Birch
the second planet in order from the sun and the nearest one to the earth in the solar system; astronomical symbol, ♀ . Venus has also been known by the names Morning Star, Hesperus, Vesper, Evening Star, Phosphorus, and Lucifer. Its mean distance from the sun is 108 million km (0.723 astronomical unit). The sidereal period measures 224 days, 16 hours, 49 minutes, and 8 seconds. To the observer on the earth, the angular distance from Venus to the sun does not exceed 48°, as a result of which the planet is visible only during a certain period after sunset (evening star) or shortly before sunrise (morning star). Venus is the brightest celestial object (after the sun and moon) in the terrestrial sky. At maximum brightness it attains a stellar magnitude of -4.4. The phases of Venus (discovered by Galileo in 1610) may be observed with the naked eye by persons with exceptionally good vision. The planet’s angular diameter at inferior conjunction reaches 64″. According to terrestrial radar observations, its average radius is 6,050 ± 0.5 km and its deviation from sphericity, ± 3 km; its mass is 1/408,522 ± 3 that of the sun and 0.9528 that of the earth.
Observed from the earth, Venus appears to be covered by a dense cloud cover having high reflectance (spherical albedo, 0.6) and lacking permanent markings. Using a few dark and bright markings noticeable on the cloud cover, principally in the wavelength range of 300-400 nanometers (3,000-4,000 angstroms), a rotation period of approximately four days has been established. (The direction of rotation is retrograde, that is, contrary to the motion of the planets around the sun.) The rotation period of the solid body of the planet, determined from radar observations, is 243 ± 0.18 days (the direction of rotation is also retrograde), while the axis of rotation is inclined to the plane of the orbit at an angle no greater than 2°. It is possible that the observed four-day rotation period of the cloud layer may be explained by atmospheric currents having an approximate velocity of 100 m/sec, which in the earth’s atmosphere is typical for altitudes of 50-60 km.
The existence of the Venusian atmosphere was first established by M. V. Iomonosov from observations of the transit of Venus across the disk of the sun in 1761.
The presence of carbon dioxide (C02) in the Venusian atmosphere has been reliably established by spectroscopic means. Carbon monoxide (CO), steam (H20), oxygen (02), hydrogen chloride (HCl), and hydrogen fluoride (HF) possibly exist in the layer above the clouds. It is supposed that the planet’s clouds consist of aqueous ice crystals. Information on the atmospheric layer below the clouds, obtained from terrestrial optical observations, is practically nonexistent.
According to observations in the radio-frequency and infrared regions of the spectrum, Venus’ brightness temperature is strongly dependent on the wavelength in which observations are conducted (see Table 1).
|Table 1. Approximate course of Venus’ brightness temperature|
|Infrared region ...............||~240|
Measurements in the infrared region of the spectrum pertain to the upper layers of the cloud cover. Maximum temperatures are apparently near the wavelength λ = 6 cm; around λ = 70 cm, the temperature, slowly changing, approaches 500-450° K. (In all cases, the temperature is averaged over the disk.) The phase change is small in the millimeter range (amplitude, approximately 10 percent) in the centimeter and decimeter ranges, it is within the limits of measurement error. The most widespread explanation for the distribution of the brightness temperature over the spectrum is the notion of the planet’s hot surface (approximately 600-700° K), whose radiation in the short and long waves is absorbed by the atmosphere. It is presumed that the high temperature of the surface is due to the greenhouse effect created by the Venusian atmosphere. Direct measurements, first made on Oct. 18, 1967, in the lower atmosphere by the Soviet unmanned interplanetary probe Venera 4 and confirmed by measurements of stations Venera 5, Venera 6, and Venera 7 (May 16, 1969, May 17, 1969, and Dec. 15, 1970), have shown that the temperature increases as the surface is approached by a gradient close to that of the adiabatic curve, and that the pressure at the surface exceeds several meganewtons/m2 (several tens of kilograms-force/cm2). According to direct investigations, the Venusian atmosphere consists principally of carbon dioxide gas, with an admixture of a small quantity of water (approximately 0.1 percent) and oxygen.
A model of the atmosphere constructed according to the data obtained from the earth as well as direct measurements leads to the conclusion that the average temperature on the surface of Venus is approximately 750° K at a pressure of approximately 10 meganewtons/m2 (100 kgf/cm2).
The surface of the planet is apparently solid; it is somewhat less pitted than that of the moon. Radar observations reveal isolated areas of increased reflectance, perhaps associated with the topography of the surface.
REFERENCESSharonov, V. V. Planeta Venera.Moscow, 1965.
Kuz’min, A. D. Radiofizicheskie issledovaniia Venery.Moscow, 1967.
Moroz, V. I. Fizika planet.Moscow, 1967.
Brandt, J., and P. Hodge. Astrofizika solnechnoi sistemy.Moscow, 1967. (Translated from English.)
G. A. LEIKIN