Bailly 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 is located near the south-west limb 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 ...

. It was named after French astronomer Jean S. Bailly. The oblique viewing angle gives the crater a foreshortened appearance, and the location near the limb can limit visibility due to

libration In lunar astronomy, libration is the wagging or wavering of the Moon perceived by Earth-bound observers and caused by changes in their perspective. It permits an observer to see slightly different hemispheres of the surface at different tim ...

. The most favorable time for viewing this feature is near the

full moon The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic coordinate system, ecliptic longitudes of the Sun and Moon opp ...

when the

terminator Terminator may refer to: Science and technology Genetics * Terminator (genetics), the end of a gene for transcription * Terminator technology, proposed methods for restricting the use of genetically modified plants by causing second generation s ...

is crossing the crater wall.

Description

This is the largest crater on the near side of the Moon. In area it is comparable in size to a small

mare A mare is an adult female horse or other equine. In most cases, a mare is a female horse over the age of three, and a filly is a female horse three and younger. In Thoroughbred horse racing, a mare is defined as a female horse more than four ...

. It lies north of the crater

Le Gentil Guillaume Joseph Hyacinthe Jean-Baptiste Le Gentil de la Galaisière (, 12 September 1725 – 22 October 1792) was a French astronomer who discovered several nebulae and was appointed to the Royal Academy of Sciences. He made unsuccessful attemp ...

and east of Hausen. Further west of Bailly are the (unofficially named) Montes Dörfel mountains. Bailly's uneven crater floor has remained free of

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 ...

flooding, and it is covered with a multitude of ridges and craters. The entire crater has been battered and worn, and the outer

rampart Rampart may refer to: * Rampart (fortification), a defensive wall or bank around a castle, fort or settlement Rampart may also refer to: * "O'er the Ramparts We Watched" is a key line from "The Star-Spangled Banner", the national anthem of the ...

s are eroded and in some places have even been worn away by myriad impacts. If the crater ever possessed a central peak, it is no longer discernible. Due to its current condition, observers have termed this feature a 'field of ruins'. Due to the size and the worn state of this crater, it is estimated to be more than 3 billion years old, and is part of the

Nectarian system The Nectarian Period of the lunar geologic timescale runs from 3920 million years ago to 3850 million years ago. It is the period during which the Nectaris Basin and other major basins were formed by large impact events. Ejecta from Nectaris fo ...

Satellite craters

The south-eastern part of the crater is home to two notable craters, designated Bailly A and Bailly B. These craters overlap, and Bailly A lies across the rim of Bailly's mountainous wall. Selenographer

Giovanni Battista Riccioli Giovanni Battista Riccioli, SJ (17 April 1598 – 25 June 1671) was an Italian astronomer and a Catholic priest in the Jesuit order. He is known, among other things, for his experiments with pendulums and with falling bodies, for his discussion ...

named Bailly B, ''Bartolus'' for fellow Ferrarese Jesuit

Daniello Bartoli Daniello Bartoli, SJ (; 12 February 160813 January 1685) was an Italian Jesuit writer and historiographer, celebrated by the poet Giacomo Leopardi as the "Dante of Italian prose" Ferrara He was born in Ferrara. His father, Tiburzio was a chemis ...

(1608-1685) in his Almagestum novum (1651). Ewen A. Whitaker: ''Mapping and Naming the Moon, a history of lunar cartography and nomenclature'', page 211. The name was not recognized by the

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

References

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External links

* {{Craters on the Moon: A–B Impact craters on the Moon Nectarian