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 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 at the southern fringes of the

Oceanus Procellarum Oceanus Procellarum ( la, Ōceanus procellārum, lit=Ocean of Storms) 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 Proc ...

, in the western hemisphere 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 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 entere ...

. 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 moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

, leaving a dark surface due to the low

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

. 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, southeas ...

, 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 wid ...

, 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