Rhaeticus (crater)
Encyclopedia
Rhaeticus is a lunar
crater
that lies astride the equator
of the Moon
, on the southeast edge of the Sinus Medii
. To the north-northwest is the crater Triesnecker
, and due south can be found the worn remnant of the walled plain Hipparchus
. The crater was named for Georg Joachim von Lauchen
, also known as Rheticus.
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 that is slightly elongated in the north-south direction. The interior has been resurfaced by lava
, 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.
Running southwest from Rhaeticus to the crater Réaumur
is a long rille
, 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.
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
that lies astride the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, on the southeast edge of the Sinus Medii
Sinus Medii
Sinus Medii is a small lunar mare that is located 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 Moon's near side, and it is the point closest to the Earth...
. To the north-northwest is the crater Triesnecker
Triesnecker (crater)
Triesnecker is a prominent lunar impact crater that is located in the Sinus Medii, near the central part of the Moon's near side. It is located to the north-northwest of the crater Rhaeticus, and to the east-southeast of the flooded Murchison....
, and due south can be found the worn remnant of the walled plain Hipparchus
Hipparchus (lunar crater)
Hipparchus is the degraded remnant of a lunar crater. It is located to the southeast of Sinus Medii, near the center of the visible Moon. To the south is the prominent crater Albategnius, and to the southwest lies Ptolemaeus, a feature of comparable dimensions to Hipparchus. Horrocks lies entirely...
. The crater was named for Georg Joachim von Lauchen
Georg Joachim Rheticus
Georg Joachim von Lauchen, also known as Rheticus , was a mathematician, cartographer, navigational-instrument maker, medical practitioner, and teacher. He is perhaps best known for his trigonometric tables and as Nicolaus Copernicus's sole pupil...
, also known as Rheticus.
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 that is slightly elongated in the north-south direction. The interior has been resurfaced by lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
, 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.
Running southwest from Rhaeticus to the crater Réaumur
Réaumur (crater)
Réaumur is the remains of a lunar crater located on the southern edge of Sinus Medii. It lies to the northwest of the large walled plain Hipparchus, and east of Flammarion. To the south is Gyldén, and farther to the south-southwest is Ptolemaeus....
is a long rille
Rille
Rille is typically used to describe any of the long, narrow depressions in the lunar surface that resemble channels. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length...
, 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
Lunar geologic timescale
The lunar geological timescale divides the history of Earth's Moon into five generally recognized periods: the Copernican, Eratosthenian, Imbrian , Nectarian, and Pre-Nectarian...
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 mid-point that is closest to Rhaeticus.| Rhaeticus | Latitude | Longitude | Diameter |
|---|---|---|---|
| A | 1.8° N | 5.2° E | 11 km |
| B | 1.7° N | 6.8° E | 6 km |
| D | 0.9° N | 6.2° E | 7 km |
| E | 0.1° S | 6.0° E | 5 km |
| F | 0.1° S | 6.5° E | 18 km |
| G | 1.0° N | 6.4° E | 6 km |
| H | 1.0° S | 5.4° E | 6 km |
| J | 0.7° S | 3.2° E | 4 km |
| L | 0.2° N | 3.6° E | 14 km |
| M | 1.0° N | 3.8° E | 7 km |
| N | 1.2° N | 4.2° E | 12 km |