Rhaeticus is a

lunar Lunar most commonly means "of or relating to the Moon". Lunar may also refer to: Arts and entertainment * ''Lunar'' (series), a series of video games * "Lunar" (song), by David Guetta * "Lunar", a song by Priestess from the 2009 album ''Prior t ...

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

that lies astride the

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...

of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

, on the southeast edge of the

Sinus Medii Sinus Medii (Latin ''sinus mediī'' "Middle Bay") is a small lunar mare. It takes its name from its location at the intersection of the Moon's equator and prime meridian; as seen from the Earth, this feature is located in the central part of the ...

. To the north-northwest is the crater Triesnecker, and due south can be found the worn remnant of the walled plain

Hipparchus Hipparchus (; el, Ἵππαρχος, ''Hipparkhos''; BC) was a Greek astronomer, geographer, and mathematician. He is considered the founder of trigonometry, but is most famous for his incidental discovery of the precession of the equi ...

. The crater was named after Austrian astronomer

Georg Joachim Rheticus Georg Joachim de Porris, also known as Rheticus ( /ˈrɛtɪkəs/; 16 February 1514 – 5 December 1576), was a mathematician, astronomer, cartographer, navigational-instrument maker, medical practitioner, and teacher. He is perhaps best known for ...

.''Autostar Suite Astronomer Edition''. CD-ROM. Meade, April 2006.

Description

The outer wall of Rhaeticus is heavily disintegrated, with rifts and notches in the northeast. The wall is most intact along the eastern face, while in the northwest it is little more than a low rise in the surface. There is also a low cut in the south-southeast wall. The overall shape of the rim is that of a rough

hexagon In geometry, a hexagon (from Ancient Greek, Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple polygon, simple (non-self-intersecting) hexagon is 720°. Regular hexa ...

that is slightly elongated in the north–south direction. The interior has been resurfaced by

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

, and only a few low rises remain in the surface. Beginning at the crest of the eastern wall is a chain of craterlets that continue to the east-northeast for about a crater diameter.Wlasuk, Peter T. (2000). ''Observing the Moon''. Springer. . Running southwest from Rhaeticus to the crater Réaumur is a long

rille Rille (German for 'groove') is typically used to describe any of the long, narrow depressions in the surface of the Moon that resemble channels. The Latin term is ''rima'', plural ''rimae''. Typically, a rille can be several kilometers wid ...

, which is difficult to make out near Rhaeticus because of the group of mountains at that crater's southwest. The crater itself is 43 kilometers wide at one diameter and 49 kilometers long at another. It is from the Pre-Imbrian period, which lasted from 4.55 to 3.85 billion years ago.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Rhaeticus. Rhaeticus sattelite craters map

Rhaeticus A crater 4102 h1.jpg, Lunar Orbiter 4 image of Rhaeticus A

References

External links

Rhaeticus
at the Moon Wiki * {{cite web, last = Wood , first = Chuck , date = February 2, 2006 , url = http://www.lpod.org/?m=20060209 , title = Layers of History , publisher = Lunar Photo of the Day , url-status=dead, archiveurl=https://web.archive.org/web/20110614233616/http://www.lpod.org/?m=20060209, archivedate=June 14, 2011 Impact craters on the Moon