An Etymological Dictionary of Astronomy and Astrophysics
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The Sun's apparent path in the sky relative to the stars in the course of a year. It is also the projection of the Earth's orbital plane onto the → celestial sphere. Because of the inclination of the → Earth's rotation axis, the ecliptic is tilted by about 23.4° with respect to the → celestial equator, an angle known as the → obliquity of the ecliptic. The ecliptic crosses the celestial equator at the → equinoxes.

From L. ecliptica linea "path of eclipses," so called because eclipses happen only when the Moon is near this path, from eclipsis, → eclipse.

Hurpeh "sun path," from hur "sun," variant xor, cognate with Gk. helios, → Sun, + peh "path, way," from O.Pers. paθi- "path, way;" Av. paθ-, variants paθi-, paθā-, pantay-; Mid/Mod.Pers. pand "path, advice, councel;" Khotanese pande "road, path;" Ossetic fœndœg "path, road;" cf. Skt. pánthā- "road, path, course;" Gk. patos "path, way;" L. pons "bridge, path;" E. find; PIE base *pent- "to go, to tread."

One of the two coordinates in the → ecliptic system; the angle measured from the ecliptic, positive toward the north.

→ ecliptic; → latitude.

One of the two coordinates in the → ecliptic system; the angle measured eastwards along the ecliptic from 0° to 360°, with the origin at the → vernal equinox.

→ ecliptic; → longitude.

The plane of Earth's orbit around the Sun.

→ ecliptic, → plane.

A catalog of fields along the → ecliptic observed by the → K2 mission. The catalog is hosted at the → Mikulski Archive for Space Telescopes (MAST).

→ ecliptic; → plane; → input; → catalogue.

Either of the two points on the celestial sphere that are 90° above and below the plane of ecliptic. The north ecliptic pole lies in → Draco, and the south ecliptic pole in → Dorado. Due to → precession, the → celestial pole moves in a circle around the ecliptic poles once every 25,800 years.

→ ecliptic, → pole.

Coordinate system with the ecliptic as the fundamental plane.

→ ecliptic; → system.

The farthest distance from a → lunar orbit node within which, if the Moon happens to be at full, a lunar eclipse may occur. The lunar ecliptic limit extends about 12° on each side of the node.

→ lunar; → ecliptic; → limit.

The angle between the Earth's → equatorial plane and the → ecliptic. Its present value is 23°26'13.5'' (or 23.43708 degrees). The effects of → precession and → nutation cause it to change between extreme values of 22.1 and 24.5 degrees over a period of approximately 41,000 years. It is currently decreasing.

→ obliquity; → ecliptic.

The component of general precession caused by the gravitational attraction of the planets on the Earth's center of mass. It causes the equinox to move eastward by about 0''.12 per year in the opposite direction to the → precession of the equator. This terminology replaces → planetary precession, according to an IAU resolution adopted in August 2006.

→ precession; → ecliptic.

The greatest angular distance from a → lunar orbit node within which a → solar eclipse may occur when the Sun and Moon are in conjunction there. The solar ecliptic limit extends about 17° on each side of the node.

→ solar; → ecliptic; → limit.