20 Massalia
A three dimensional model of 20 Massalia, based on its light curve.
|
|
| Discovery | |
|---|---|
| Discovered by | Annibale de Gasparis |
| Discovery date | September 19, 1852 |
| Designations | |
| MPC designation | (20) Massalia |
| Pronunciation | /məˈseɪliə/ mə-SAY-lee-ə |
|
Named after
|
Marseille |
| none | |
| Main belt (Massalia family) | |
| Orbital characteristics | |
| Epoch October 22, 2004 (JD 2453300.5) | |
| Aphelion | 411.911 Gm (2.753 AU) |
| Perihelion | 308.699 Gm (2.064 AU) |
| 360.305 Gm (2.408 AU) | |
| Eccentricity | 0.143 |
| 1365.261 d (3.74 a) | |
|
Average orbital speed
|
19.09 km/s |
| 161.641° | |
| Inclination | 0.707° |
| 206.530° | |
| 255.578° | |
| Physical characteristics | |
| Dimensions | 160×145×132 km 145 km (mean) 160×145×130 km |
| Mass | 5.67×1018 kg 5.2×1018 kg |
|
Mean density
|
3.54±0.85 g/cm³ |
| 0.054 m/s² | |
| 0.093 km/s | |
| 0.3374 d (8.098 h) | |
| Albedo | 0.210 (geometric) |
| Temperature | ~174 K max: 265 K (-8°C) |
|
Spectral type
|
S |
| 8.3 to 12.0 | |
| 6.50 | |
| 0.186" to 0.058" | |
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.
Massalia is an S-type asteroid. 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 piles. In 1998, Bange estimated Massalia to have a mass of 5.2×1018 kg assuming that 4 Vesta has 1.35×10−10solar 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.
In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty.
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