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  2. Mercury (planet) - Wikipedia

    en.wikipedia.org/wiki/Mercury_(planet)

    Mercury attains an inferior conjunction (nearest approach to Earth) every 116 Earth days on average, [4] but this interval can range from 105 days to 129 days due to the planet's eccentric orbit. Mercury can come as near as 82,200,000 km (0.549 astronomical units; 51.1 million miles) to Earth, and that is slowly declining: The next approach to ...

  3. Transit of Mercury - Wikipedia

    en.wikipedia.org/wiki/Transit_of_Mercury

    A transit of Mercury across the Sun takes place when the planet Mercury passes directly between the Sun and a superior planet. During a transit, Mercury appears as a tiny black dot moving across the Sun as the planet obscures a small portion of the solar disk. Because of orbital alignments, transits viewed from Earth occur in May or November.

  4. Outline of Mercury (planet) - Wikipedia

    en.wikipedia.org/wiki/Outline_of_Mercury_(planet)

    Mercury – smallest and innermost planet in the Solar System. Its orbital period (about 88 Earth days) is less than any other planet in the Solar System. Seen from Earth, it appears to move around its orbit in about 116 days. It has no known natural satellites. It is named after the Roman deity Mercury, the messenger to the gods.

  5. Tidal locking - Wikipedia

    en.wikipedia.org/wiki/Tidal_locking

    In Mercury's case, the planet completes three rotations for every two revolutions around the Sun, a 3:2 spin–orbit resonance. In the special case where an orbit is nearly circular and the body's rotation axis is not significantly tilted, such as the Moon, tidal locking results in the same hemisphere of the revolving object constantly facing ...

  6. Retrograde and prograde motion - Wikipedia

    en.wikipedia.org/wiki/Retrograde_and_prograde_motion

    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). It may also describe other motions such as precession or nutation of an object's rotational axis. Prograde or direct motion is more normal motion in the same ...

  7. Tests of general relativity - Wikipedia

    en.wikipedia.org/wiki/Tests_of_general_relativity

    Albert Einstein proposed [3][4] three tests of general relativity, subsequently called the "classical tests" of general relativity, in 1916: the perihelion precession of Mercury 's orbit. the deflection of light by the Sun. the gravitational redshift of light. In the letter to The Times (of London) on November 28, 1919, he described the theory ...

  8. Apparent retrograde motion - Wikipedia

    en.wikipedia.org/wiki/Apparent_retrograde_motion

    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. Direct motion or prograde motion is motion in the same direction as other bodies. While the terms direct and prograde are equivalent in this context, the former is the ...

  9. Orbital inclination - Wikipedia

    en.wikipedia.org/wiki/Orbital_inclination

    Orbits. The inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the orbital plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planet's equator.