Zodiac

The zodiac is an area of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and visible planets are also within the belt of the zodiac.The English word zodiac derives from zōdiacus, the Latinized form of the Ancient Greek zōidiakòs kýklos (ζῳδιακός κύκλος), meaning 'cycle or circle of little animals'. Zōidion (ζῴδιον) is the diminutive of zōion (ζῷον, 'animal'). The name reflects the prominence of animals (and mythological hybrids) among the twelve signs.The zodiac was in use by the Roman era, based on concepts inherited by Hellenistic astronomy from Babylonian astronomy of the Chaldean period (mid-1st millennium BC), which, in turn, derived from an earlier system of lists of stars along the ecliptic. The construction of the zodiac is described in Ptolemy's vast 2nd century AD work, the Almagest.The division of the ecliptic into the zodiacal signs originates in Babylonian ('Chaldean') astronomy during the first half of the 1st millennium BC. The zodiac draws on stars in earlier Babylonian star catalogues, such as the MUL.APIN catalogue, which was compiled around 1000 BC. Some of the constellations can be traced even further back, to Bronze Age (First Babylonian dynasty) sources, including Gemini 'The Twins', from MAŠ.TAB.BA.GAL.GAL 'The Great Twins', and Cancer 'The Crab', from AL.LUL 'The Crayfish', among others.What follows is a list of the signs of the modern zodiac (with the ecliptic longitudes of their first points), where 0° Aries is understood as the vernal equinox, with their Latin, Greek, Sanskrit, and Babylonian names (but note that the Sanskrit and the Babylonian name equivalents (after c.500 BC) denote the constellations only, not the tropical zodiac signs). Also, the 'English translation' is not usually used by English speakers. The 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.:25 Thus, Virgo takes up five times as much ecliptic longitude as Scorpius. The zodiacal signs are an abstraction from the physical constellations, and each represent exactly one twelfth of the full circle, or the longitude traversed by the Sun in about 30.4 days.The following table compares the Gregorian dates on which the Sun entersThe zodiac system was developed in Babylonia, some 2,500 years ago, during the 'Age of Aries'. At the time, it is assumed, the precession of the equinoxes was unknown. 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.Astronomically, the zodiac defines a belt of space extending 9° either side of the ecliptic, within which the orbits of the Moon and the principal planets remain. It is a feature of a celestial coordinate system centered upon the ecliptic, (the plane of the Earth's orbit and the Sun's apparent path), by which celestial longitude is measured in degrees east of the vernal equinox (the ascending intersection of the ecliptic and equator). Stars within the zodiac are subject to occultations by the moon and other solar system bodies. 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.In Unicode, the symbols of zodiac signs are encoded in block 'Miscellaneous Symbols':