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Of the inner planets, Mercury and Venus have no natural satellites; Earth has one large natural satellite, known as the Moon; and Mars has two tiny natural satellites, Phobos and Deimos. The giant planets have extensive systems of natural satellites, including half a dozen comparable in size to Earth's Moon: the four Galilean moons , Saturn's ...
Mercury is the closest planet to the Sun and lacks any natural satellites.An undiscovered moon orbiting the planet was hypothesized to exist in the early 1970s, but it turned out to be misinterpreted data from the star 31 Crateris. [1]
Mercury, the smallest and innermost planet, has no moons, or at least none that can be detected to a diameter of 1.6 km (1.0 mi). [2] For a very short time in 1974, Mercury was thought to have a moon. Venus also has no moons, [3] though reports of a moon around Venus have circulated since the 17th century.
The Roman numbering system for satellites arose with the very first discovery of natural satellites other than Earth's Moon: Galileo referred to the Galilean moons as I through IV (counting from Jupiter outward), refusing to adopt the names proposed by his rival Simon Marius. Similar numbering schemes naturally arose with the discovery of ...
Mercury is the first planet from the Sun and the smallest in the Solar System. In English, it is named after the ancient Roman god Mercurius , god of commerce and communication, and the messenger of the gods. Mercury is classified as a terrestrial planet, with roughly the same surface gravity as Mars.
A subsatellite, also known as a submoon or informally a moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet. [3] It is inferred from the empirical study of natural satellites in the Solar System that subsatellites may be rare, albeit possible, elements of planetary systems. In the Solar System ...
The English proper name for Earth's natural satellite is typically written as Moon, with a capital M. [19] [20] The noun moon is derived from Old English mōna, which stems from Proto-Germanic *mēnōn, [21] which in turn comes from Proto-Indo-European *mēnsis 'month' [22] (from earlier *mēnōt, genitive *mēneses) which may be related to the verb 'measure' (of time).
The distinction between a satellite and a classical planet was not recognized until after the heliocentric model of the Solar System was established. When in 1610 Galileo discovered the first satellites of another planet (the four Galilean moons of Jupiter), he referred to them as "four planets flying around the star of Jupiter at unequal intervals and periods with wonderful swiftness."