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The orbit of the Moon is a nearly circular ellipse about the Earth (the semimajor and semiminor axes are 384,400 km and 383,800 km, respectively: a difference of only 0.16%). The equation of the ellipse yields an eccentricity of 0.0549 and perigee and apogee distances of 362,600 km (225,300 mi) and 405,400 km (251,900 mi) respectively (a ...
The Moon is Earth 's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Tidal forces between Earth and the Moon have over time synchronized the Moon's orbital period ( lunar month) with its rotation period ( lunar day) at 29.5 Earth days, causing the same side of the Moon ...
Lunar day. A full lunar day observed from the Earth, where orbital libration causes the apparent wobble. A lunar day is the time it takes for Earth 's Moon to complete on its axis one synodic rotation, meaning with respect to the Sun. Informally, a lunar day and a lunar night is each approx. 14 Earth days. The formal lunar day is therefore the ...
As each day is divided into 24 hours, the first hour of a day is ruled by the planet three places down in the Chaldean order from the planet ruling the first hour of the preceding day; [2] i.e. a day with its first hour ruled by the Sun ("Sunday") is followed by a day with its first hour ruled by the Moon ("Monday"), followed by Mars ("Tuesday ...
They are respectively the fourth-, sixth-, first-, and third-largest natural satellites in the Solar System, containing approximately 99.997% of the total mass in orbit around Jupiter, while Jupiter is almost 5,000 times more massive than the Galilean moons. [ note 3] The inner moons are in a 1:2:4 orbital resonance.
Lunar orbit. Orion capsule of Artemis 1 above the Moon in December 2022. In astronomy and spaceflight, a lunar orbit (also known as a selenocentric orbit) is an orbit by an object around Earth's Moon. In general these orbits are not circular. When farthest from the Moon (at apoapsis) a spacecraft is said to be at apolune, apocynthion, or aposelene.
11.8[9] Phobos(/ˈfoʊbəs/; systematic designation: Mars I) is the innermost and larger of the two natural satellites of Mars,[10]the other being Deimos. The two moons were discovered in 1877 by American astronomer Asaph Hall. It is named after Phobos, the Greek godof fear and panic, who is the son of Ares(Mars) and twin brother of Deimos.
Proxima Centauri b is the closest exoplanet to Earth, at a distance of about 4.2 ly (1.3 parsecs). It orbits Proxima Centauri every 11.186 Earth days at a distance of about 0.049 AU, over 20 times closer to Proxima Centauri than Earth is to the Sun. As of 2021, it is unclear whether it has an eccentricity but Proxima Centauri b is unlikely to have any obliquity.