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  2. Venus - Wikipedia

    en.wikipedia.org/wiki/Venus

    This allows Venus to be the most accessible destination and a useful gravity assist waypoint for interplanetary flights from Earth. Venus figures prominently in human culture and in the history of astronomy. Orbiting inferiorly (inside of Earth's orbit), it always appears close to the Sun in Earth's sky, as either a "morning star" or an ...

  3. Deferent and epicycle - Wikipedia

    en.wikipedia.org/wiki/Deferent_and_epicycle

    Babylonian observations showed that for superior planets the planet would typically move through in the night sky slower than the stars. Each night the planet appeared to lag a little behind the stars, in what is called prograde motion. Near opposition, the planet would appear to reverse and move through the night sky faster than the stars for ...

  4. Retrograde and prograde motion - Wikipedia

    en.wikipedia.org/wiki/Retrograde_and_prograde_motion

    Six of the planets also rotate about their axis in this same direction. The exceptions – the planets with retrograde rotation – are Venus and Uranus. Venus's axial tilt is 177°, which means it is rotating almost exactly in the opposite direction to its orbit. Uranus has an axial tilt of 97.77°, so its axis of rotation is approximately ...

  5. 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 ...

  6. 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.

  7. Axial precession - Wikipedia

    en.wikipedia.org/wiki/Axial_precession

    Earth rotates (white arrows) once a day around its rotational axis (red); this axis itself rotates slowly (white circle), completing a rotation in approximately 26,000 years [1] In astronomy , axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis .

  8. Meridian (astronomy) - Wikipedia

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

    For a location not on this axis, there is a unique meridian plane in this axial-pencil through that location. The intersection of this plane with Earth's surface defines two geographical meridians (either one east and one west of the prime meridian , or else the prime meridian itself and its anti-meridian), and the intersection of the plane ...

  9. Apparent retrograde motion - Wikipedia

    en.wikipedia.org/wiki/Apparent_retrograde_motion

    An animation explaining why the planet Mercury may appear to move "backwards", or retrograde across Earth's sky. Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point.