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  2. Opposition (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Opposition_(astronomy)

    The astronomical symbol for opposition is ☍ (U+260D). () Seen from a superior planet, an inferior planet on the opposite side of the Sun is in superior conjunction with the Sun. An inferior conjunction occurs when the two planets align on the same side of the Sun. At inferior conjunction, the superior planet is "in opposition" to the Sun as ...

  3. Kepler's laws of planetary motion - Wikipedia

    en.wikipedia.org/wiki/Kepler's_laws_of_planetary...

    Kepler's first law placing the Sun at one of the foci of an elliptical orbit Heliocentric coordinate system (r, θ) for ellipse. Also shown are: semi-major axis a , semi-minor axis b and semi-latus rectum p ; center of ellipse and its two foci marked by large dots.

  4. Retrograde and prograde motion - Wikipedia

    en.wikipedia.org/wiki/Retrograde_and_prograde_motion

    Retrograde orbit: the satellite (red) orbits in the direction opposite to the rotation of its primary (blue/black) Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure).

  5. Solar conjunction - Wikipedia

    en.wikipedia.org/wiki/Solar_conjunction

    Solar conjunction between Earth and Mars. Solar conjunction generally occurs when a planet or other Solar System object is on the opposite side of the Sun from the Earth.From an Earth reference, the Sun will pass between the Earth and the object.

  6. Solar System - Wikipedia

    en.wikipedia.org/wiki/Solar_System

    The principal component of the Solar System is the Sun, a G-type main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally. [37] The Sun's four largest orbiting bodies, the giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%.

  7. Deferent and epicycle - Wikipedia

    en.wikipedia.org/wiki/Deferent_and_epicycle

    In the Hipparchian, Ptolemaic, and Copernican systems of astronomy, the epicycle (from Ancient Greek ἐπίκυκλος (epíkuklos) 'upon the circle', meaning "circle moving on another circle") [1] was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets.

  8. Perturbation (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Perturbation_(astronomy)

    In astronomy, perturbation is the complex motion of a massive body subjected to forces other than the gravitational attraction of a single other massive body. [1] The other forces can include a third (fourth, fifth, etc.) body, resistance, as from an atmosphere, and the off-center attraction of an oblate or otherwise misshapen body.

  9. Planetary system - Wikipedia

    en.wikipedia.org/wiki/Planetary_system

    An artist's concept of a planetary system. A planetary system is a set of gravitationally bound non-stellar bodies in or out of orbit around a star or star system.Generally speaking, systems with one or more planets constitute a planetary system, although such systems may also consist of bodies such as dwarf planets, asteroids, natural satellites, meteoroids, comets, planetesimals [1] [2] and ...