Billy 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 depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

that is located at the southern fringes of the

Oceanus Procellarum Oceanus Procellarum ( ; from ) is a vast lunar mare on the western edge of the near side of the Moon. It is the only one of the lunar maria to be called an "Oceanus" (ocean), due to its size: Oceanus Procellarum is the largest of the maria ("s ...

, in the western hemisphere of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

. It was named after French mathematician

Jacques de Billy : ''For the English patristic scholar and Benedictine abbot, see Jacques de Billy (abbot) (1535–1581).'' Jacques de Billy (March 18, 1602 – January 14, 1679) was a French Jesuit mathematician. Born in Compiègne, he subsequently enter ...

. It lies to the southeast of the similar-sized crater Hansteen, and west-southwest of the flooded Letronne. The interior floor of Billy has been flooded by

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

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 Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

, leaving a dark surface due to the low

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

. The portion of the rim remaining above the surface is narrow and low, with a thin inner wall. Only a few tiny craterlets mark the interior. To the north of the crater is a triangular mountainous formation named

Mons Hansteen Mons Hansteen is a mountain on the Moon, also known as Hansteen Alpha (α), named after Christopher Hansteen. It is roughly triangular in shape and occupies an area about 30 km across on the western margin of Oceanus Procellarum, southea ...

, from the nearby crater. Southeast of Billy is a

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 w ...

, designated Rima Billy, that runs 70 kilometers to the south.

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 Billy.

References

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External links

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