ekliptik

Ekliptik, in astronomy, refers to the ecliptic: the plane of Earth's orbit around the Sun as projected onto the celestial sphere, and the Sun’s apparent yearly path through the sky. It serves as a convenient reference plane for locating objects and defining the seasons, since the Sun, Moon, and planets move close to this plane.

The ecliptic is inclined to the celestial equator by about 23.44 degrees. It intersects the equator at two points, the vernal (spring) and autumnal (fall) equinoxes. The angle between the ecliptic and the equator, called the obliquity of the ecliptic, varies slightly over long timescales, currently around 23.4 degrees, and it changes over tens of thousands of years.

In addition to the Sun’s apparent path, the ecliptic is a baseline for celestial coordinates. Ecliptic longitude and latitude measure positions along and perpendicular to the ecliptic. The vernal equinox serves as the zero point for longitude. The orientation of the ecliptic relative to the background stars changes slowly due to the precession of the equinoxes, shifting the coordinates over millennia.

The Moon’s orbit is inclined about 5 degrees to the ecliptic, and the major planets also orbit near this plane, which explains why the zodiac lies along the ecliptic. Historically, the ecliptic was central to calendars and astronomy and remains a standard reference plane in modern celestial mechanics and ephemerides.