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The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. [ 1 ] [ 2 ] [ a ] From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars . [ 3 ]
Because it is a right-handed system, ecliptic longitude is measured positive eastwards in the fundamental plane (the ecliptic) from 0° to 360°. Because of axial precession , the ecliptic longitude of most "fixed stars" (referred to the equinox of date) increases by about 50.3 arcseconds per year, or 83.8 arcminutes per century, the speed of ...
The geocentric ecliptic system was the principal coordinate system for ancient astronomy and is still useful for computing the apparent motions of the Sun, Moon, and planets. [3] It was used to define the twelve astrological signs of the zodiac , for instance.
For a satellite orbiting a planet, the plane of reference is usually the plane containing the planet's equator. For planets in the Solar System, the plane of reference is usually the ecliptic, the plane in which the Earth orbits the Sun. [1] [2] This reference plane is most practical for Earth-based observers. Therefore, Earth's inclination is ...
The North Ecliptic Pole is located near the Cat's Eye Nebula and the South Ecliptic Pole is located near the Large Magellanic Cloud. It is impossible anywhere on Earth for either ecliptic pole to be at the zenith in the night sky. By definition, the ecliptic poles are located 90° from the Sun's position.
Earth's orbital plane is known as the ecliptic plane, and Earth's tilt is known to astronomers as the obliquity of the ecliptic, being the angle between the ecliptic and the celestial equator on the celestial sphere. [6] It is denoted by the Greek letter Epsilon ε. Earth currently has an axial tilt of about 23.44°. [7]
The plane of the ecliptic (grey) is defined by the Earth's orbit around the Sun, and is distinct from the plane of the celestial sphere 's equator (green), which is permanently tilted 23.4 degrees with respect to the ecliptic. To an observer on Earth, this means that the path the Sun appears to follow upon the celestial sphere is not a straight ...
Conjunctions between a planet inside the orbit of Earth (Venus or Mercury) and a planet outside are a bit more complicated. As the outer planet swings around from being in opposition to the Sun to being east of the Sun, then in superior conjunction with the Sun, then west of the Sun, and back to opposition, it will be in conjunction with Venus ...