Bessel is a small lunar

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 is located in the southern half of the Mare Serenitatis

Mare Serenitatis

Mare Serenitatis is a lunar mare that sits just to the east of Mare Imbrium on the Moon.It is located within the Serenitatis basin, which is of the Nectarian epoch. The material surrounding the mare is of the Lower Imbrian epoch, while the mare material is of the Upper Imbrian epoch...

. Despite its small size, this is the largest crater to lie entirely within the mare

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

. It lies to the north-northeast of the crater Menelaus

Menelaus (crater)

Menelaus is a young lunar impact crater located on the southern shore of Mare Serenitatis near the eastern end of the Montes Hæmus mountain range. The crater was named after the jilted king of Sparta from the Iliad. To the southwest is the small crater Auwers, and to the southwest is the even...

.

This crater is circular and bowl-shaped with a rim that has a higher albedo

Albedo

Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

 than the floor or the surrounding mare. The outer rim is not significantly worn, and there are no features of note on the interior, apart from some slumping of material from the inner walls to the floor. Bessel is not of sufficient size to have developed the terrace structures of larger craters. It was named after Friedrich Wilhelm Bessel.

A large ray

Ray system

A ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking a bit like many thin spokes coming from the hub of a wheel. The rays can extend for lengths up to several times the diameter of their originating crater, and are often accompanied by...

, most likely from Tycho

Tycho (crater)

Tycho is a prominent lunar impact crater located in the southern lunar highlands, named after the Danish astronomer Tycho Brahe . To the south is the crater Street; to the east is Pictet, and to the north-northeast is Sasserides. The surface around Tycho is replete with craters of various sizes,...

, crosses the mare from north to south, passing Bessel's western side.

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 Bessel.

Bessel	Latitude	Longitude	Diameter
D	27.3° N	19.9° E	5 km
F	21.2° N	13.8° E	1 km
G	21.1° N	14.7° E	1 km
H	25.7° N	20.0° E	4 km

The following craters have been renamed by the IAU

International Astronomical Union

The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

.

• Bessel A — See Sarabhai (crater)
  Sarabhai (crater)
  Sarabhai is a small, circular, bowl-shaped crater on the Mare Serenitatis, in the northeast quadrant of the Moon. The formation is relatively isolated, being located to the northeast of the crater Bessel. It lies along a wrinkle ridge designated the Dorsum Azara.This crater was previously...
  
  .
• Bessel E — See Bobillier (crater)
  Bobillier (crater)
  Bobillier is a tiny, cup-shaped lunar impact crater in the southwest part of Mare Serenitatis. It lies to the north-northwest of the crater Bessel. To the south and west is a wrinkle ridge designated Dorsum Buckland....
  
  .