Massalia, minor planet designation 20 Massalia, is a stony asteroid and the parent body of the

Massalia family The Massalia family (adj. ''Massalian''; FIN: 404) is a family of asteroids in the inner asteroid belt, named after its parent body, 20 Massalia. It consists of S-type asteroids with very low inclinations, straddling the 1:2 resonances with ...

located in the inner region of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, c ...

, approximately in diameter. Discovered by Italian astronomer

Annibale de Gasparis Annibale de Gasparis (9 November 1819, Bugnara – 21 March 1892, Naples; ) was an Italian astronomer, known for discovering asteroids and his contributions to theoretical astronomy. Biography De Gasparis was born in 1819 in Bugnara to Ang ...

on 19 September 1852, it was named for the French city of

Marseille Marseille ( , , ; also spelled in English as Marseilles; oc, Marselha ) is the prefecture of the French department of Bouches-du-Rhône and capital of the Provence-Alpes-Côte d'Azur region. Situated in the camargue region of southern Fra ...

, from which the independent discover

Jean Chacornac Jean Chacornac (21 June 1823 – 23 September 1873) was a French astronomer and discoverer of a comet and several asteroids. He was born in Lyon and died in Saint-Jean-en-Royans, southeastern France. Working in Marseille and Paris, he discov ...

sighted it the following night.

Classification and orbit

''Massalia'' is the namesake and the

parent body In meteoritics, a parent body is the celestial body from which originates a meteorite or a class of meteorites. Identification The easiest way to correlate a meteorite with a parent body is when the parent body still exists. This is the case fo ...

of the

(), a very large inner belt asteroid family consisting of stony asteroids with very low inclinations. It is by far the largest body in this family. The remaining family members are fragments ejected by a cratering event on Massalia. It orbits the Sun in the

inner Interior may refer to: Arts and media * ''Interior'' (Degas) (also known as ''The Rape''), painting by Edgar Degas * ''Interior'' (play), 1895 play by Belgian playwright Maurice Maeterlinck * ''The Interior'' (novel), by Lisa See * Interior de ...

main-belt at a distance of 2.1–2.8 AU once every 3 years and 9 months (1,366 days; semi-major axis of 2.41 AU). Its orbit has 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 ...

of 0.14 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 1 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...

Physical characteristics

''Massalia'' has an above-average density for S-type asteroids, similar to the density of silicate rocks. As such, it appears to be a solid un-fractured body, a rarity among asteroids of its size. Apart from the few largest bodies over 400 km in diameter, such as 1 Ceres and

4 Vesta Vesta ( minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of . It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, t ...

, most asteroids appear to have been significantly fractured, or are even

rubble pile In astronomy, a rubble pile is a celestial body that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. Rubble piles have low density because there are large cavities between the ...

s. In 1998, Bange estimated Massalia to have a mass of 5.2 kg assuming that 4 Vesta has 1.35 solar mass. The mass of Massalia is dependent on the mass of 4 Vesta and

perturbation Perturbation or perturb may refer to: * Perturbation theory, mathematical methods that give approximate solutions to problems that cannot be solved exactly * Perturbation (geology), changes in the nature of alluvial deposits over time * Perturbat ...

of 44 Nysa. Lightcurve analysis indicates that Massalia's pole points towards either

ecliptic coordinates The ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small Solar System bodi ...

(β, λ) = (45°, 10°) or (β, λ) = (45°, 190°) with a 10° uncertainty. This gives an

axial tilt In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orb ...

of 45°in both cases. The shape reconstruction from lightcurves has been described as quite spherical with large planar, nonconvex parts of the surface. In 1988 a search for satellites or dust orbiting this asteroid was performed using the

UH88 The University of Hawai'i 88-inch (2.24-meter) telescope—called UH88, UH2.2, or simply 88 by members of the local astronomical community—is situated at the Mauna Kea Observatories and operated by the University's Institute for Astronomy. It ...

telescope at the

Mauna Kea Observatories The Mauna Kea Observatories (MKO) are a group of independent astronomical research facilities and large telescope observatories that are located at the summit of Mauna Kea on the Big Island of Hawaiʻi, United States. The facilities are located ...

, but the effort came up empty.

Discovery

Massalia was discovered on 19 September 1852, by

at Naples Observatory in Italy, and also found independently the next night by

at Marseilles Observatory, France. It was Chacornac's discovery that was announced first. In the nineteenth century the variant spelling Massilia was often used. Asteroids discovered prior to Massalia were assigned iconic symbols, like the ones traditionally used to designate the planets. However, astronomers had begun to phase out this practice with the discovery of 16 Psyche in March 1852, and 20 Massalia (being the first object in the Solar System with a non-mythological name) was the first asteroid that was not assigned an iconic symbol.

References

External links

*
Elements and Ephemeris for (20) Massalia
from the Minor Planet Center * * {{DEFAULTSORT:000020 Massalia asteroids Massalia Massalia S-type asteroids (Tholen) S-type asteroids (SMASS) 18520919