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A lunar node is either of the two orbital nodes of the Moon, that is, the two points at which the orbit of the Moon intersects the ecliptic. The ascending (or north) node is where the Moon moves into the northern ecliptic hemisphere, while the descending (or south) node is where the Moon enters the southern ecliptic hemisphere.
An eclipse of the Moon or Sun can occur when the nodes align with the Sun, roughly every 173.3 days. Lunar orbit inclination also determines eclipses; shadows cross when nodes coincide with full and new moon when the Sun, Earth, and Moon align in three dimensions. In effect, this means that the "tropical year" on the Moon is only 347 days long.
Another type of lunar orbit precession is that of the plane of the Moon's orbit. The period of the lunar nodal precession is defined as the time it takes the ascending node to move through 360° relative to the vernal equinox (autumnal equinox in the Southern Hemisphere). It is about 18.6 years and the direction of motion is westward, i.e., in ...
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Animation of the Moon as it cycles through its phases, as seen from the Northern Hemisphere. The apparent wobbling of the Moon is known as libration.
Lunar nearside with major maria and craters labeled. Lunar maria (singular mare) are large, dark, regions of the Moon.They do not contain any water, but are believed to have been formed from molten rock from the Moon's mantle coming out onto the surface of the Moon.
Strictly speaking, the lunar standstill is a moving position in the sky relative to the direction of Earth's axis and to the rotation of the Moon's orbital nodes (lunar nodal precession) once every 18.6 years. The standstill position does not persist over the two weeks that the Moon takes to move from its maximum (positive) declination to its ...
The lunar night lasts approximately 14 Earth days, during which the Moon experiences extreme cold temperatures and complete darkness. To ensure the survivability and functionality of the lunar ...
Sunrise occurs at the prime meridian when the Lunar phase reaches First Quarter, after one fourth of a lunar day. At this location the selenographic colongitude at sunrise is defined as 0°. Thus, by the time of the Full Moon the colongitude increases to 90°; at Last Quarter it is 180°, and at the New Moon the colongitude reaches 270°.