Lunar radius in the context of "Ray system"

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⭐ Core Definition: Lunar radius

The Moon is the only natural satellite of Earth. It orbits around Earth at an average distance of 384,399 kilometres (238,854 mi), a distance roughly 30 times the width of Earth. It completes an orbit (lunar month) in relation to Earth and the Sun (synodically) every 29.5 days. The Moon and Earth are bound by gravitational attraction, which is stronger on the sides facing each other. The resulting tidal forces are the main driver of Earth's tides, and have pulled the Moon to always face Earth with the same near side. This tidal locking effectively synchronizes the Moon's rotation period (lunar day) to its orbital period (lunar month).

In geophysical terms, the Moon is a planetary-mass object or satellite planet. Its mass is 1.2% that of the Earth, and its diameter is 3,474 km (2,159 mi), roughly one-quarter of Earth's (about as wide as the contiguous United States). Within the Solar System, it is larger and more massive than any known dwarf planet, and the fifth-largest and fifth-most massive moon, as well as the largest and most massive in relation to its parent planet. Its surface gravity is about one-sixth of Earth's, about half that of Mars, and the second-highest among all moons in the Solar System after Jupiter's moon Io. The body of the Moon is differentiated and terrestrial, with only a minuscule hydrosphere, atmosphere, and magnetic field. The lunar surface is covered in regolith dust, which mainly consists of the fine material ejected from the lunar crust by impact events. The lunar crust is marked by impact craters, with some younger ones featuring bright ray-like streaks. The Moon was volcanically active until 1.2 billion years ago, surfacing lava mostly on the thinner near side of the Moon, filling ancient craters, which through cooling formed the today prominently visible dark plains of basalt called maria ('seas'). The origin of the Moon is not clear, although it has been hypothesized to have formed out of material from Earth, ejected by a giant impact into Earth of a Mars-sized body named Theia 4.51 billion years ago, not long after Earth's formation.

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Lunar radius in the context of Lunar distance

The instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. In contrast, the Lunar distance (LD or ), or Earth–Moon characteristic distance, is a unit of measure in astronomy. More technically, it is the semi-major axis of the geocentric lunar orbit. The average lunar distance is approximately 385,000 km (239,000 mi), or 1.3 light-seconds. It is roughly 30 times Earth's diameter and a non-stop plane flight traveling that distance would take more than two weeks. Around 389 lunar distances make up an astronomical unit (roughly the distance from Earth to the Sun).

Lunar distance is commonly used to express the distance to near-Earth object encounters. Lunar semi-major axis is an important astronomical datum. It has implications for testing gravitational theories such as general relativity and for refining other astronomical values, such as the mass, radius, and rotation of Earth. The measurement is also useful in measuring the lunar radius, as well as the distance to the Sun.

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LINKED FROM (PARENTS)
← Lunar distance ← Lunar distance (astronomy)
LINKS TO (CHILDREN)
Natural satellite → Earth → Orbit of the Moon → Lunar distance → Earth diameter → Orbital period → Lunar month → Lunation → Gravity → Tidal force → Tide → Near side of the Moon → Tidal locking → Rotation period (astronomy) → Lunar day → Geophysical definition of planet → Planetary-mass object → Satellite planet → Contiguous United States → Solar System → List of Solar System objects by size → Dwarf planet → Primary body → Surface gravity → Mars → Jupiter → Io (moon) → Planetary differentiation → Terrestrial planet → Hydrosphere → Atmosphere of the Moon → Magnetic field of the Moon → Lunar surface → Lunar regolith → Ejecta blanket → Lunar crust → Impact event → Impact crater → Ray system → Basalt → Lunar mare → Origin of the Moon → Giant-impact hypothesis → Theia (planet) → Age of Earth →