120 Lachesis
Lachesis (minor planet designation: 120 Lachesis) is a large main-belt asteroid. It was discovered by French astronomer Alphonse Borrelly on April 10, 1872, and independently by German-American astronomer Christian Heinrich Friedrich Peters on April 11, 1872, then named after Lachesis, one of the Moirai, or Fates, in Greek mythology. A Lachesean occultation 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 184 × 144 km.
3D convex shape model of 120 Lachesis | |
| Discovery | |
|---|---|
| Discovered by | Alphonse Borrelly |
| Discovery date | 10 April 1872 |
| Designations | |
MPC designation | (120) Lachesis |
| Pronunciation | /ˈlækɪsɪs/ LAK-iss-iss |
Named after | Lachesis |
Alternative designations | A872 GB; 1910 CF; 1918 UB |
Minor planet category | Main belt |
| Adjectives | Lachesian (/læˈkiːʃ(i)ən, ləˈkiːʒən/ la-KEE-sh(ee-)ən, lə-KEE-zhən) |
| Orbital characteristics | |
| Epoch 31 July 2016 (JD 2457600.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 143.70 yr (52485 d) |
| Aphelion | 3.2814 AU (490.89 Gm) |
| Perihelion | 2.95390 AU (441.897 Gm) |
Semi-major axis | 3.11767 AU (466.397 Gm) |
| Eccentricity | 0.052528 |
Orbital period (sidereal) | 5.50 yr (2010.7 d) |
Average orbital speed | 16.86 km/s |
Mean anomaly | 56.2095° |
Mean motion | 0° 10m 44.558s / day |
| Inclination | 6.9643° |
Longitude of ascending node | 341.193° |
| 232.822° | |
| Earth MOID | 1.95464 AU (292.410 Gm) |
| Jupiter MOID | 1.72275 AU (257.720 Gm) |
| TJupiter | 3.204 |
| Physical characteristics | |
| Dimensions | 155.132±1.133 km (IRAS) |
| Mass | 5.5×1018 kg |
Equatorial surface gravity | 0.0487 m/s2 |
Equatorial escape velocity | 0.0920 km/s |
Synodic rotation period | 46.551 h (1.9396 d) |
| 0.0463±0.002 | |
| Temperature | ~158 K |
| C | |
| 7.75 | |
This body is orbiting the Sun with a period of 5.50 years and an eccentricity (ovalness) of 0.05. The orbital plane is inclined by 7° to the plane of the ecliptic. Photometric observations of this asteroid were made in early 2009 at the Organ Mesa Observatory in Las Cruces, New Mexico. The resulting light curve shows a synodic rotation period of 46.551 ± 0.002 hours with a brightness variation of 0.14 ± 0.02 in magnitude. It is a very slow rotator with the longest rotation period of an asteroid more than 150 km in diameter. As a primitive C-type asteroid it is probably composed of carbonaceous material.