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  2. Ecliptic coordinate system - Wikipedia

    en.wikipedia.org/wiki/Ecliptic_coordinate_system

    The origin is the Sun's center, the plane of reference is the ecliptic plane, and the primary direction (the x-axis) is the March equinox. A right-handed rule specifies a y-axis 90° to the east on the fundamental plane. The z-axis points toward the north ecliptic pole. The reference frame is relatively stationary, aligned with the March equinox.

  3. Axial tilt - Wikipedia

    en.wikipedia.org/wiki/Axial_tilt

    The angles for Earth, Uranus, and Venus are approximately 23°, 97°, and 177° respectively. In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbital plane ...

  4. Orbit of Venus - Wikipedia

    en.wikipedia.org/wiki/Orbit_of_Venus

    Representation of Venus (yellow) and Earth (blue) circling around the Sun. Venus and its rotation in respect to its revolution. Venus has an orbit with a semi-major axis of 0.723 au (108,200,000 km; 67,200,000 mi), and an eccentricity of 0.007.

  5. Ecliptic - Wikipedia

    en.wikipedia.org/wiki/Ecliptic

    Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth's equator with respect to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic. It is about 23.4° and is currently decreasing 0.013 degrees (47 arcseconds) per hundred years because of planetary perturbations.

  6. 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.

  7. Venus - Wikipedia

    en.wikipedia.org/wiki/Venus

    The highest point on Venus, Maxwell Montes, is therefore the coolest point on Venus, with a temperature of about 655 K (380 °C; 715 °F) and an atmospheric pressure of about 4.5 MPa (45 bar). [ 127 ] [ 128 ] In 1995, the Magellan spacecraft imaged a highly reflective substance at the tops of the highest mountain peaks, a " Venus snow " that ...

  8. Analemma - Wikipedia

    en.wikipedia.org/wiki/Analemma

    The change of position is a result of the shifting of the angle in the sky of the path that the Sun takes in respect to the stars (the ecliptic). The diagram resembles a figure eight. Globes of the Earth often display an analemma as a two-dimensional figure of equation of time ("sun fast") vs. declination of the Sun.

  9. Planetary coordinate system - Wikipedia

    en.wikipedia.org/wiki/Planetary_coordinate_system

    Chart of lunar maria with lines of longitude and latitude. The prime meridian is the centre of the near side of the Moon.. A planetary coordinate system (also referred to as planetographic, planetodetic, or planetocentric) [1] [2] is a generalization of the geographic, geodetic, and the geocentric coordinate systems for planets other than Earth.