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The Moon has a solid iron-rich inner core with a radius possibly as small as 240 kilometres (150 mi) and a fluid outer core primarily made of liquid iron with a radius of roughly 300 kilometres (190 mi). Around the core is a partially molten boundary layer with a radius of about 500 kilometres (310 mi).
The Moon's elongation is its angular distance east of the Sun at any time. At new moon, it is zero and the Moon is said to be in conjunction. At full moon, the elongation is 180° and it is said to be in opposition. In both cases, the Moon is in syzygy, that is, the Sun, Moon and Earth are nearly aligned.
Early attempts to measure the distance to the Moon exploited observations of a lunar eclipse combined with knowledge of Earth's radius and an understanding that the Sun is much further than the Moon. By observing the geometry of a lunar eclipse, the lunar distance can be calculated using trigonometry .
The moon is the namesake of Europa, in Greek mythology the daughter of the Phoenician king of Tyre. ... with an orbital radius of about 670,900 km.
The mean radius in astronomy is a measure for the size of planets and small Solar System bodies. Alternatively, the closely related mean diameter ( D {\displaystyle D} ), which is twice the mean radius, is also used.
Schematic illustration of the internal structure of the Moon. Several lines of evidence imply that the lunar core is small, with a radius of about 350 km or less. [5] The diameter of the lunar core is only about 20% the diameter of the Moon itself, in contrast to about 50% as is the case for most other terrestrial bodies.
Although the Moon's Hill sphere extends to a radius of 60,000 km (37,000 mi), [6] the gravity of Earth intervenes enough to make lunar orbits unstable at a distance of 690 km (430 mi). [7] The Lagrange points of the Earth-Moon system can provide stable orbits in the lunar vicinity, such as halo orbits and distant retrograde orbits.
Ganymede is the only Galilean moon of Jupiter named after a male figure—like Io, Europa, and Callisto, he was a lover of Zeus. In English, the Galilean satellites Io, Europa and Callisto have the Latin spellings of their names, but the Latin form of Ganymede is Ganymēdēs , which would be pronounced / ˌ ɡ æ n ɪ ˈ m iː d iː z / . [ 38 ]