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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. Exploration of Mercury - Wikipedia

    en.wikipedia.org/wiki/Exploration_of_Mercury

    The exploration of Mercury has a minor role in the space interests of the world. It is the least explored inner planet. [1] As of 2015, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER made three flybys before entering orbit around Mercury. [2]

  4. 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 ...

  5. Vulcan (hypothetical planet) - Wikipedia

    en.wikipedia.org/wiki/Vulcan_(hypothetical_planet)

    Vulcan (hypothetical planet) Vulcan / ˈvʌlkən / [2] was a proposed planet that some pre-20th century astronomers thought existed in an orbit between Mercury and the Sun. Speculation about, and even purported observations of, intermercurial bodies or planets date back to the beginning of the 17th century. The case for their probable existence ...

  6. 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.

  7. Astronomy on Mercury - Wikipedia

    en.wikipedia.org/wiki/Astronomy_on_Mercury

    This is due to the high eccentricity of Mercury's orbit around the Sun. [1] A 19th century depiction of the apparent size of the Sun as seen from the Solar System's planets (incl. 72 Feronia and the then most outlying known asteroid, here called Maximiliana and now called 65 Cybele). Due to tidal locking, three rotations of Mercury, is equal to ...

  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. MESSENGER - Wikipedia

    en.wikipedia.org/wiki/MESSENGER

    MESSENGER. MESSENGER was a NASA robotic space probe that orbited the planet Mercury between 2011 and 2015, studying Mercury's chemical composition, geology, and magnetic field. [9][10] The name is a backronym for "Mercury Surface, Space Environment, Geochemistry, and Ranging", and a reference to the messenger god Mercury from Roman mythology.