21 Lutetia
Lutetia (minor planet designation: 21 Lutetia) is a large M-type asteroid in the main asteroid belt. It measures about 100 kilometers in diameter (120 km along its major axis). It was discovered in 1852 by Hermann Goldschmidt, and is named after Lutetia, the Latin name of Paris.
Rosetta image of 21 Lutetia at closest approach | |
| Discovery | |
|---|---|
| Discovered by | Hermann M. S. Goldschmidt |
| Discovery date | 15 November 1852 |
| Designations | |
MPC designation | (21) Lutetia |
| Pronunciation | /ljuːˈtiːʃiə/ |
Named after | Paris (Latin: Lutētia) |
Minor planet category | Main belt |
| Adjectives | Lutetian |
| Orbital characteristics | |
| Epoch May 31, 2020 (JD 2459000.5) | |
| Aphelion | 2.833 AU |
| Perihelion | 2.037 AU |
Semi-major axis | 2.435 AU |
| Eccentricity | 0.16339 |
Orbital period (sidereal) | 3.80 yr (1388.1 d) |
Mean anomaly | 87.976° |
| Inclination | 3.064° |
Longitude of ascending node | 80.867° |
| 249.997° | |
| Physical characteristics | |
| Dimensions | c/a = 0.65±0.03 (121±1) × (101±1) × (75±13) km |
Mean radius | 49±1 km |
| Volume | (5.0±0.4)×1014 m3 |
| Mass | (1.700±0.017)×1018 kg |
Mean density | 3.45±0.21 g/cm3 3.4±0.3 g/cm3 |
Synodic rotation period | 0.3402 d (8.1655 h) |
| 96° | |
North pole right ascension | 51.8 ± 0.4° |
North pole declination | +10.8 ± 0.4° |
| 0.19 ± 0.01 (geometrical) 0.073 ± 0.002 (bond) | |
| Temperature | 170–245 K |
| M (Tholen) | |
| 9.25 to 13.17 | |
| 7.29 | |
Lutetia has an irregular shape and is heavily cratered, with the largest impact crater reaching 45 km in diameter. The surface is geologically heterogeneous and is intersected by a system of grooves and scarps, which are thought to be fractures. It has a high overall bulk density, suggesting that it is made of metal-rich rock.
The Rosetta probe passed within 3,162 km (1,965 mi) of Lutetia in July 2010. It was the largest asteroid visited by a spacecraft until Dawn arrived at Vesta in July 2011.