120 Lachesis is a large

main-belt asteroid The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

. It was discovered by French astronomer

Alphonse Borrelly Alphonse Louis Nicolas Borrelly (December 8, 1842 – February 28, 1926) was a French astronomer born in Roquemaure, Gard. He joined the Marseille Observatory in 1864. In the course of his career, he discovered a number of asteroids and comets, ...

on April 10, 1872, and independently by German-American astronomer

Christian Heinrich Friedrich Peters Christian Heinrich Friedrich Peters (September 19, 1813 – July 18, 1890) was a German–American astronomer and professor at Hamilton College, New York, and a pioneer in the study and visual discovery of asteroids. His name is often given as ...

on April 11, 1872, then named after

Lachesis Lachesis ( ; ; from , 'to obtain by lot, by fate, or by the will of the gods'), in ancient Greek religion, was the middle of the Three Fates, or Moirai; the others were her sisters, Clotho and Atropos. Normally seen clothed in white, Laches ...

, one of the

Moirai In ancient Greek religion and Greek mythology, mythology, the Moirai ()often known in English as the Fateswere the personifications of fate, destiny. They were three sisters: Clotho (the spinner), Lachesis (mythology), Lachesis (the allotter ...

, or Fates, in

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

. A Lachesean

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

of a star occurred in 1999 and was confirmed visually by five observers and once photoelectrically, with the chords yielding an estimated elliptical cross-section of . This body is orbiting the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

with a period of 5.50 years and an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

(ovalness) of 0.05. The

orbital plane The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) a ...

is inclined by 7° to the

plane of the ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. From the perspe ...

. Photometric observations of this asteroid were made in early 2009 at the Organ Mesa Observatory in

Las Cruces, New Mexico Las Cruces (; ; lit. 'the crosses') is the List of municipalities in New Mexico, second-most populous city in the U.S. state of New Mexico and the county seat, seat of Doña Ana County, New Mexico, Doña Ana County. As of the 2020 United States ce ...

. The resulting

light curve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

shows a synodic

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

of 46.551 ± 0.002 hours with a brightness variation of 0.14 ± 0.02 in

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

. It is a very slow rotator with the longest

of an asteroid more than 150 km in diameter. As a primitive

C-type asteroid C-type (carbonaceous ) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

it is probably composed of

carbonaceous Carbonaceous refers to something relating to, containing, or composed of carbon. It is a descriptor used for the attribute of any substance rich in carbon. Particularly, ''carbonaceous hydrocarbons'' are very unsaturated, high- molecular-weight h ...

material.

References

External links

* * 000120 Discoveries by Alphonse Borrelly Named minor planets 000120 000120 18720410 {{C-beltasteroid-stub