120 Lachesis
Main-belt asteroid
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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.[5] 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 Ã 144 km.[6]
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3D convex shape model of 120 Lachesis | |
| Discovery | |
|---|---|
| Discovered by | Alphonse Borrelly |
| Discovery date | 10 April 1872 |
| Designations | |
| (120) Lachesis | |
| Pronunciation | /Ëlækɪsɪs/ LAK-iss-iss[1] |
Named after | Lachesis |
| A872 GB; 1910 CF; 1918 UB | |
| Main belt | |
| Adjectives | Lachesian (/læËkiËÊ(i)Én, lÉËkiËÊÉn/ la-KEE-sh(ee-)Én, lÉ-KEE-zhÉn) |
| Orbital characteristics[2] | |
| 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) |
| 3.11767 AU (466.397 Gm) | |
| Eccentricity | 0.052528 |
| 5.50 yr (2010.7 d) | |
Average orbital speed | 16.86 km/s |
| 56.2095° | |
| 0° 10m 44.558s / day | |
| Inclination | 6.9643° |
| 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)[2] |
| Mass | 5.5Ã1018 kg |
Equatorial surface gravity | 0.0487 m/s2 |
Equatorial escape velocity | 0.0920 km/s |
| 46.551 h (1.9396 d)[2][3] | |
| 0.0463±0.002[2] | |
| Temperature | ~158 K |
| C[4] | |
| 7.75[2] | |
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.[3] It is a very slow rotator[7] with the longest rotation period of an asteroid more than 150 km in diameter.[8] As a primitive C-type asteroid[4] it is probably composed of carbonaceous material.
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