20 Massalia
Encyclopedia
20 Massalia is a large and fairly bright main-belt asteroid
. It is also the largest member of the Massalia family
of asteroids. Its name is the Greek
name for Marseille
, the city from which one of the two independent co-discovers, Jean Chacornac
, first sighted it.
. It orbits at very low inclination in the intermediate main belt, and is by far the largest asteroid in the Massalia family
. The remaining family members are fragments ejected by a cratering event on Massalia.
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
, most asteroids appear to have been significantly fractured, or are even rubble pile
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
of 44 Nysa
.
Lightcurve analysis indicates that Massalia's pole points towards either ecliptic coordinates
(β, λ) = (45°, 10°) or (β, λ) = (45°, 190°) with a 10° uncertainty. This gives an axial tilt
of 45°in both cases. The shape reconstruction from lightcurves has been described as quite spherical with large planar, nonconvex parts of the surface.
on September 19, 1852 in Naples
, and also found independently the next night by J. Chacornac
in Marseilles. It was Chacornac's discovery that was announced first. In the nineteenth century the variant spelling Massilia was often used.
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
. It is also the largest member of the Massalia family
Massalia family
The Massalia family of asteroids is a grouping of S-type asteroids in the inner main belt at very low inclination. About 0.8% of known asteroids belong to this family.-Characteristics:...
of asteroids. Its name is the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
name for Marseille
Marseille
Marseille , known in antiquity as Massalia , is the second largest city in France, after Paris, with a population of 852,395 within its administrative limits on a land area of . The urban area of Marseille extends beyond the city limits with a population of over 1,420,000 on an area of...
, the city from which one of the two independent co-discovers, Jean Chacornac
Jean Chacornac
Jean Chacornac was a French astronomer.He was born in Lyon and died in St Jean en Royans. Working in Marseille and Paris, he discovered six asteroids. The asteroid 1622 Chacornac and the crater Chacornac on the Moon are named in his honour....
, first sighted it.
Characteristics
Massalia is an S-type asteroidS-type asteroid
S-type asteroids are of a stony composition, hence the name. Approximately 17% of asteroids are of this type, making it the second most common after the C-type.-Characteristics:...
. It orbits at very low inclination in the intermediate main belt, and is by far the largest asteroid in the Massalia family
Massalia family
The Massalia family of asteroids is a grouping of S-type asteroids in the inner main belt at very low inclination. About 0.8% of known asteroids belong to this family.-Characteristics:...
. The remaining family members are fragments ejected by a cratering event on Massalia.
Massalia has an above-average density for S-type asteroids, similar to the density of silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
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
1 Ceres
Ceres, formally 1 Ceres, is the smallest identified dwarf planet in the Solar System and the only one in the asteroid belt. With a diameter of about 950 km, Ceres is by far the largest and most-massive asteroid, comprising about a third of the mass of the asteroid belt. Discovered on 1 January 1801...
and 4 Vesta
4 Vesta
Vesta, formally designated 4 Vesta, is one of the largest asteroids, with a mean diameter of about . It was discovered by Heinrich Wilhelm Olbers on March 29, 1807, and is named after the Roman virgin goddess of home and hearth, Vesta....
, most asteroids appear to have been significantly fractured, or are even rubble pile
Rubble pile
In astronomy, rubble pile is the informal name for an object that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity...
s. In 1998, Bange estimated Massalia to have a mass of 5.2 kg assuming that 4 Vesta has 1.35 solar mass
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. The mass of Massalia is dependent on the mass of 4 Vesta and perturbation
Perturbation (astronomy)
Perturbation is a term used in astronomy in connection with descriptions of the complex motion of a massive body which is subject to appreciable gravitational effects from more than one other massive body....
of 44 Nysa
44 Nysa
44 Nysa is a large and very bright main-belt asteroid, and the brightest member of the Nysian asteroid family. It is classified as a rare class E asteroid and is probably the largest of this type .-Discovery:...
.
Lightcurve analysis indicates that Massalia's pole points towards either ecliptic coordinates
Ecliptic coordinate system
The ecliptic coordinate system is a celestial coordinate system that uses the ecliptic for its fundamental plane. The ecliptic is the path that the sun appears to follow across the celestial sphere over the course of a year. It is also the intersection of the Earth's orbital plane and the celestial...
(β, λ) = (45°, 10°) or (β, λ) = (45°, 190°) with a 10° uncertainty. This gives an axial tilt
Axial tilt
In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...
of 45°in both cases. The shape reconstruction from lightcurves has been described as quite spherical with large planar, nonconvex parts of the surface.
Discovery
Massalia was discovered by A. de GasparisAnnibale de Gasparis
Annibale de Gasparis was an Italian astronomer. From 1864 to 1889 he was the director of the Astronomical Observatory of Capodimonte in Naples.He won the Gold Medal of the Royal Astronomical Society in 1851....
on September 19, 1852 in Naples
Naples
Naples is a city in Southern Italy, situated on the country's west coast by the Gulf of Naples. Lying between two notable volcanic regions, Mount Vesuvius and the Phlegraean Fields, it is the capital of the region of Campania and of the province of Naples...
, and also found independently the next night by J. Chacornac
Jean Chacornac
Jean Chacornac was a French astronomer.He was born in Lyon and died in St Jean en Royans. Working in Marseille and Paris, he discovered six asteroids. The asteroid 1622 Chacornac and the crater Chacornac on the Moon are named in his honour....
in Marseilles. It was Chacornac's discovery that was announced first. In the nineteenth century the variant spelling Massilia was often used.
External links
- shape model deduced from lightcurve
- Elements and Ephemeris for (20) Massalia from the Minor Planet Center.
- Orbital simulation from JPL (Java) / Ephemeris