Zodiac

a zone within the CELESTIAL SPHERE which contains the paths of the planet, the Moon and the Sun. It is divided into the signs of the zodiac, named after the constellations.

Taken from Dictionary of Science

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In astronomy, the zodiac is the ring of constellations that lines the ecliptic, which is the apparent path of the Sun across the sky over the course of the year. The Moon and planets also lie within the ecliptic, and so are also within the constellations of the zodiac. In astrology, the zodiac denotes those signs that divide the ecliptic into twelve equal zones of celestial longitude. As such, the zodiac is a celestial coordinate system, to be more precise, an ecliptic coordinate system, taking the ecliptic as the origin of latitude, and the position of the sun at vernal equinox as the origin of longitude.

It is known to have been 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 Almagest (2nd century AD). It was originally described in Rigveda. The term zodiac may also refer to the region of the celestial sphere encompassing the paths of the Moon and the planets corresponding to the band of about eight arc degrees above and below the ecliptic. The zodiac of a given planet is the band that contains the path of that particular body; e.g., the "zodiac of the Moon" is the band of five degrees above and below the ecliptic. By extension, the "zodiac of the comets" may refer to the band encompassing most short-period comets.

The term zodiac derives from Latin zōdiacus, in turn from the Greek ζωδιακός κύκλος (zōdiakos kuklos), meaning circle of animals, derived from ζώδιον (zōdion), the diminutive of ζῶον (zōon) animal. The name is motivated by the fact that half of the signs of the classical Greek zodiac are represented as animals as well as two mythological hybrids.

Although the zodiac remains the basis of the ecliptic coordinate system in use in astronomy besides the equatorial one, the term and the names of the twelve signs are today mostly associated with horoscopic astrology.

Taken from Wikipedia

Lagrangian Points

in particular, with respect to the Earth and Moon, the locations where the gravitational forces are equal and so objects positioned at such points remain fixed. There are five such points between the Earth and Moon.

Taken from Dictionary of Science

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The Lagrangian points (pronounced /ləˈgrandʒiən/; also Lagrange points, L-points, or libration points), are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects (such as a satellite with respect to the Earth and Moon). The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centripetal force required to rotate with them. They are analogous to geostationary orbits in that they allow an object to be in a "fixed" position in space rather than an orbit in which its relative position changes continuously.

More technically and precisely, Lagrangian points are the stationary solutions of the circular restricted three-body problem. For example, given two massive bodies in circular orbits around their common center of mass, there are five positions in space where a third body, of comparatively negligible mass, could be placed which would then maintain its position relative to the two massive bodies. As seen in a rotating reference frame with the same period as the two co-orbiting bodies, the gravitational fields of two massive bodies combined with the centrifugal force are in balance at the Lagrangian points, allowing the third body to be stationary with respect to the first two bodies.

Taken from Wikipedia

Eclipse

the total or partial disappearance of one astronomical body by passing into the shadow of another. A solar eclipse occurs when the new moon passes between the earth and the sun. A lunar eclipse occurs when the moon moves into the shadow of the earth, i.e., the earth is situated between the sun and the moon.

Taken from Dictionary of Science