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  2. Moon - Wikipedia

    en.wikipedia.org/wiki/Moon

    The Moon is Earth's only natural satellite, orbiting at an average distance of 384 399 km (238,854 mi; 30 Earths across).It faces Earth always with the same side.This is a result of Earth's gravitational pull having synchronized the Moon's rotation period with its orbital period (lunar month) of 29.5 Earth days.

  3. Definition of planet - Wikipedia

    en.wikipedia.org/wiki/Definition_of_planet

    A planet is any object in orbit around the Sun with a diameter greater than 2,000 km. (Eleven votes in favor) A planet is any object in orbit around the Sun whose shape is stable due to its own gravity. (Eight votes in favor) A planet is any object in orbit around the Sun that is dominant in its immediate neighbourhood. (Six votes in favor) [48 ...

  4. Double planet - Wikipedia

    en.wikipedia.org/wiki/Double_planet

    The Moon-to-Earth mass ratio of 0.01230 (≈ 1 ⁄ 81) is also notably close to 1 when compared to all other satellite-to-planet ratios. Consequently, some scientists view the Earth–Moon system as a double planet as well, though this is a minority view.

  5. Planet - Wikipedia

    en.wikipedia.org/wiki/Planet

    The eight planets of the Solar System with size to scale (up to down, left to right): Saturn, Jupiter, Uranus, Neptune (outer planets), Earth, Venus, Mars, and Mercury (inner planets) A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. [1]

  6. Natural satellite - Wikipedia

    en.wikipedia.org/wiki/Natural_satellite

    The term satellite thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of "moon". In 1957, however, the launching of the artificial object Sputnik created a need for new terminology. [5] The terms man-made satellite and artificial moon were very quickly abandoned in favor of the simpler satellite ...

  7. Opposition (astronomy) - Wikipedia

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

    The "speed" at which a planet goes around the Sun, in terms of revolutions per time, is given by the inverse of its period, and the speed difference between two planets is the difference between these. Since the time interval between two oppositions is the time it takes for 360° to be covered by that speed difference, the average interval is:

  8. Conjunction (astronomy) - Wikipedia

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

    Visual conjunction between the Moon and the planet Venus, the two brightest objects in the night sky. In astronomy, a conjunction occurs when two astronomical objects or spacecraft appear to be close to each other in the sky. This means they have either the same right ascension or the same ecliptic longitude, usually as observed from Earth. [1] [2]

  9. Planetary differentiation - Wikipedia

    en.wikipedia.org/wiki/Planetary_differentiation

    The Moon's density is substantially less than that of Earth, due to its lack of a large iron core. [3] On Earth , physical and chemical differentiation processes led to a crustal density of approximately 2700 kg/m 3 compared to the 3400 kg/m 3 density of the compositionally different mantle just below, and the average density of the planet as a ...