Latin names are standard English usage. The zodiacal signs are distinct from the constellations associated with them, not only because of their drifting apart due to the precession of equinoxes but also because the physical constellations take up varying widths of the ecliptic, so the Sun is not in each constellation for the same amount of time. The zodiacal signs are an abstraction from the physical constellations, and each represent exactly one 12th of the full circle, or the longitude traversed by the Sun in about The path of the Sun passes through 13 constellations recognized by ancient Babylonian, Greek, and Roman astronomers including in Ptolemy 's Almagest   and the modern International Astronomical Union.
Because the Babylonians had a month lunar calendar, they chose and divided up the year evenly. The 13th was left out: Ophiuchus , the bottom part of which interjects between Scorpio and Sagittarius. Occasionally this difference between the astronomical constellations and the astrological signs is mistakenly reported in the popular press as a "change" to the list of traditional signs by some astronomical body like the IAU, NASA , or the Royal Astronomical Society. For example, in drawing a distinction between astrology and scientific astronomy, NASA notes that "No one has shown that astrology can be used to predict the future or describe what people are like based on their birth dates.
Some "parazodiacal" constellations are also touched by the paths of the planets, leading to counts of up to 25 "constellations of the zodiac". Some other constellations are also mythologically associated with the zodiacal ones: Piscis Austrinus , The Southern Fish, is attached to Aquarius. In classical maps, it swallows the stream poured out of Aquarius' pitcher, but perhaps it formerly just swam in it.
Aquila , The Eagle, was possibly associated with the zodiac by virtue of its main star, Altair. The following table compares the Gregorian dates on which the Sun enters:. The theoretical beginning of Aries is the moment of vernal equinox , and all other dates shift accordingly.
The precise Gregorian times and dates vary slightly from year to year as the Gregorian calendar shifts relative to the tropical year. Except for and , the vernal equinox has started on 20 March since , and is projected to until Because the Earth's axis is at an angle, some signs take longer to rise than others, and the farther away from the equator the observer is situated, the greater the difference. Thus, signs are spoken of as "long" or "short" ascension. The zodiac system was developed in Babylonia , some 2, years ago, during the " Age of Aries ". Contemporary use of the coordinate system is presented with the choice of interpreting the system either as sidereal , with the signs fixed to the stellar background , or as tropical , with the signs fixed to the point vector of the Sun at the March equinox.
Western astrology takes the tropical approach, whereas Hindu astrology takes the sidereal one. This results in the originally unified zodiacal coordinate system drifting apart gradually, with a clockwise westward precession of 1. For the tropical zodiac used in Western astronomy and astrology, this means that the tropical sign of Aries currently lies somewhere within the constellation Pisces " Age of Pisces ".
The sidereal coordinate system takes into account the ayanamsa , ayan meaning transit or movement , and amsa meaning small part , i. It is unclear when Indians became aware of the precession of the equinoxes, but Bhaskara 2 's 12th-century treatise Siddhanta Shiromani gives equations for measurement of precession of equinoxes, and says his equations are based on some lost equations of Suryasiddhanta plus the equation of Munjaala. The discovery of precession is attributed to Hipparchus around BC.
Ptolemy quotes from Hipparchus' now lost work entitled "On the Displacement of the Solstitial and Equinoctial Points" in the seventh book of his 2nd century astronomical text, Almagest , where he describes the phenomenon of precession and estimates its value. The principle of the vernal point acting as the first degree of the zodiac for Greek astronomers is also described in the 1st century BC astronomical text of Geminus of Rhodes. Geminus explains that Greek astronomers of his era associate the first degrees of the zodiac signs with the two solstices and the two equinoxes, in contrast to the older Chaldean Babylonian system, which placed these points within the zodiac signs.
Ptolemy also demonstrates that the principle of the tropical zodiac was well known to his predecessors within his astrological text, the Tetrabiblos , where he explains why it would be an error to associate the regularly spaced signs of the seasonally aligned zodiac with the irregular boundaries of the visible constellations:.
These events can be useful, for example, to estimate the cross-sectional dimensions of a minor planet , or check a star for a close companion. The Sun's placement upon the vernal equinox, which occurs annually around 21 March, defines the starting point for measurement, the first degree of which is historically known as the " first point of Aries ". Zodiac signs have never been used to determine the boundaries of astronomical constellations that lie in the vicinity of the zodiac, which are, and always have been, irregular in their size and shape.
The use of the zodiac as a means to determine astronomical measurement remained the main method for defining celestial positions by Western astronomers until the Renaissance, at which time preference moved to the equatorial coordinate system , which measures astronomical positions by right ascension and declination rather than the ecliptic-based definitions of celestial longitude and celestial latitude.
The word "zodiac" is also used in reference to the zodiacal cloud of dust grains that move among the planets, and the zodiacal light that originates from their scattering of sunlight. In Unicode, the symbols of zodiac signs are encoded in block "Miscellaneous Symbols": .
From Wikipedia, the free encyclopedia. This is the latest accepted revision , reviewed on 3 December For the East Asian zodiac based on the Jovian orbital cycle, see Chinese zodiac. For other uses, see zodiac disambiguation. Further information: Former constellations. Further information: Babylonian star catalogues and MUL. Main article: Astrological sign. Further information: Axial precession , Epoch astronomy , Sidereal and tropical astrology , Astrological age , and Ayanamsa. Astronomical symbols Chinese zodiac Circle of stars Cusp astrology Elements of the zodiac.
Oxford Dictionaries. Oxford University Press. Retrieved 19 September The Signs of the Zodiac. Wilcox, London, p.
See also Lankford, John; Rothenberg, Marc History of Astronomy: An Encyclopedia. Definitely this week, water-bearer!
Thursday could give you a helpful strategy to protect your heart. Prioritize your financial health this weekend by auditing your spending and setting more responsible budgets. Happy birthday, Pisces! Be sure to journal your thoughts and dreams this weekend. Type keyword s to search. Today's Top Stories.
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Your Scorpio Monthly Horoscope for December. Birth Sign Flower: Match the Aries enthusiasm and zeal with flowers the color of passion romantic or otherwise — like an anything-but-demure red tulip flower bouquet. Zodiac Sign: Even though they're best known for being as headstrong and fierce as a bull — their zodiac sign's symbol — there's an indisputable warmhearted, romantic and sensuous side to the Taurus personality as well. And, while this earth sign's also known for its well-grounded, practical sensibilities, they harbor an equally strong love for beautiful things, pleasure and comfort that enjoys being indulged.
Birth Sign Flower: Cater to the Taurus's appreciation for nature's exquisite beauty with flowers that appeal to their full range of senses — like a flower bouquet showcasing majestic lilies. Their rich symbolism will appeal to the Taurus's respect for history, and the lily's dramatic form and fragrant perfume will indulge their romantic, sensual side.
Zodiac Sign: Easily adaptable and versatile — with a lively sometimes bordering on the mischievous imagination — Geminis are one of the most creative of all the zodiac signs. Their expressive downright talkative , clever qualities make them fun-loving friends and treasured companions. Birth Sign Flower: Surprise a Gemini with a flower bouquet filled with roses — a flower that symbolizes the essence of their zodiac sign: love and companionship.
Some say that the Cancer's personality can be boiled down to one word: sensitivity — and along with this comes a patient, sociable and loving disposition. Birth Sign Flower: Let these generous spirits know how much you appreciate their compassion and thoughtfulness with a flower arrangement filled with delphinium — aptly named for their dolphin-shaped flowers an appropriate match for this water sign.
Zodiac Sign: The most dominant, spontaneously creative and extroverted of all the zodiac signs, Leos are also warmhearted, generous and loving. Strong, honorable, self-confident and dignified, those who share this birth sign think and act big — loving the limelight stealing it, if they have to. Zodiac Sign: With a penchant for detail, Virgos are often known for their meticulous and diligent personalities.
Birth Sign Flower: Surprise this otherwise practical, intellectual and serious earth sign with a flower arrangement that provokes their more lighthearted side. Romantic and charming, those born under this air sign are naturally kind and gentle. Birth Sign Flower: With their strong wooden stems and lacey, star-shaped pom-poms, hydrangeas personify the balance of opposites — a fitting choice for Libras. Zodiac Sign: Known as the most intense of the zodiac signs, Scorpios are both powerful and passionate. Their tenacity and willpower are immense, their conviction strong if not at times overwhelming , and yet Scorpios are also deeply sensitive and easily moved by their emotions.
In fact, Scorpios are said to be more likely to become geniuses than those born under any other zodiac sign.
Birth Sign Flower: Indulge the sensual and passionate Scorpio with a floral bouquet of lush red peonies. Zodiac Sign: The centaur — the horse-and-man symbol for the Sagittarius zodiac sign — represents a combination of powerful intellect teamed with physical strength and energy.
Strong, independent spirits and full of energy, Sagittarians are naturally open-minded and thirst for new ways of thinking, craving travel and exploration.