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The pterygoid hamulus is a hook-like process at the lower extremity of the medial pterygoid plate of the sphenoid bone of the skull. It is the superior origin of the pterygomandibular raphe , and the levator veli palatini muscle .
Hamulus is the diminutive – hooklet or little hook. The plural is hamuli. Adjectives are hamate and hamulate, as in "a hamulate wing-coupling", in which the wings of certain insects in flight are joined by hooking hamuli on one wing into folds on a matching wing. Hamulate can also mean "having hamuli".
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 .
Nodal precession of the lunar nodes as the Earth revolves around the Sun causes an eclipse season approximately every six months. A lunar eclipse can occur only when the full Moon is near either lunar node (within 11° 38' ecliptic longitude), while a solar eclipse can occur only when the new Moon is near either lunar node (within 17° 25').
About the fourth month, a center appears for each lingula and speedily joins the rest of the bone. The presphenoid is united to the postsphenoid about the eighth month, and at birth the sphenoid is in three pieces [Fig. 4]: a central, consisting of the body and small wings, and two lateral, each comprising a great wing and pterygoid process.
Like many of the craters on the Moon's near side, it was given its name by Giovanni Riccioli, whose 1651 nomenclature system has become standardized. [6] Riccioli awarded Copernicus a prominent crater despite the fact that, as an Italian Jesuit , he conformed with church doctrine in publicly opposing Copernicus's heliocentric system.
Longitude on the Moon is measured both east and west from its prime meridian.When no direction is specified, east is positive and west is negative. Roughly speaking, the Moon's prime meridian lies near the center of the Moon's disc as seen from Earth. For precise applications, many coordinate sys
The center rille is a challenging target for telescope observation from the Earth and described as, "notoriously hard to spot." [ 2 ] The rille itself is longer than the valley proper, at 196.65 km ± 10.98 km, and has a width of 0.58 km ± 0.09 km and depth of 77.69 m ± 28.07 m.