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  2. Kepler orbit - Wikipedia

    en.wikipedia.org/wiki/Kepler_orbit

    An elliptic Kepler orbit with an eccentricity of 0.7, a parabolic Kepler orbit and a hyperbolic Kepler orbit with an eccentricity of 1.3. The distance to the focal point is a function of the polar angle relative to the horizontal line as given by the equation ( 13 )

  3. De motu corporum in gyrum - Wikipedia

    en.wikipedia.org/wiki/De_motu_corporum_in_gyrum

    (Translation: 'The major planets orbit, therefore, in ellipses having a focus at the center of the Sun, and with their radii (vectores) drawn to the Sun describe areas proportional to the times, altogether (Latin: 'omnino') as Kepler supposed.') (This conclusion is reached after taking as initial fact the observed proportionality between square ...

  4. Orbital eccentricity - Wikipedia

    en.wikipedia.org/wiki/Orbital_eccentricity

    In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit. The eccentricity of this Kepler orbit is a non-negative number that defines its shape. The eccentricity may take the following values: Circular orbit: e = 0; Elliptic orbit: 0 < e < 1; Parabolic trajectory: e = 1; Hyperbolic trajectory: e > 1; The eccentricity e ...

  5. Ancient Greek astronomy - Wikipedia

    en.wikipedia.org/wiki/Ancient_Greek_astronomy

    Anaximander. The main features of Archaic Greek cosmology are shared with those found in ancient near eastern cosmology.They include (a flat) earth, a heaven (firmament) where the sun, moon, and stars are located, an outer ocean surrounding the inhabited human realm, and the netherworld (), the first three of which corresponded to the gods Ouranos, Gaia, and Oceanus (or Pontos).

  6. Orbit - Wikipedia

    en.wikipedia.org/wiki/Orbit

    An animation showing a low eccentricity orbit (near-circle, in red), and a high eccentricity orbit (ellipse, in purple). In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object [1] such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such ...

  7. Celestial mechanics - Wikipedia

    en.wikipedia.org/wiki/Celestial_mechanics

    Osculating orbit is the temporary Keplerian orbit about a central body that an object would continue on, if other perturbations were not present. Retrograde motion is orbital motion in a system, such as a planet and its satellites, that is contrary to the direction of rotation of the central body, or more generally contrary in direction to the ...

  8. 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.

  9. Celestial spheres - Wikipedia

    en.wikipedia.org/wiki/Celestial_spheres

    In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. [7] In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre.