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.[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 × 144 km.[6]

120 Lachesis
Discovery
Discovered byAlphonse Borrelly
Discovery date10 April 1872
Designations
(120) Lachesis
Pronunciation/ˈlækɪsɪs/[1]
Named after
Lachesis
Main belt
AdjectivesLachesian /læˈkiːʃ(i)ən, ləˈkiːʒən/
Orbital characteristics[2]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc143.70 yr (52485 d)
Aphelion3.2814 AU (490.89 Gm)
Perihelion2.95390 AU (441.897 Gm)
3.11767 AU (466.397 Gm)
Eccentricity0.052528
5.50 yr (2010.7 d)
16.86 km/s
56.2095°
0° 10m 44.558s / day
Inclination6.9643°
341.193°
232.822°
Earth MOID1.95464 AU (292.410 Gm)
Jupiter MOID1.72275 AU (257.720 Gm)
TJupiter3.204
Physical characteristics
Dimensions174.10±2.9 km (IRAS)[2]
Mass5.5×1018 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]

    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 has the longest rotation period of an asteroid more than 150 km in diameter.[7] As a primitive C-type asteroid[4] it is probably composed of carbonaceous material.

    References
    1. "Lachesis". Lexico UK Dictionary. Oxford University Press.
    2. "JPL Small-Body Database Browser: 120 Lachesis". Jet Propulsion Laboratory. Retrieved May 12, 2016.
    3. Pilcher, Frederick (July 2009), "Rotation Period Determinations for 120 Lachesis, 131 Vala 157 Dejanira, and 271 Penthesilea", The Minor Planet Bulletin, 36 (3), pp. 100–102, Bibcode:2009MPBu...36..100P.
    4. Tedesco, E. F.; et al. (February 1989), "A three-parameter asteroid taxonomy", Astronomical Journal, 97, pp. 580–606, Bibcode:1989AJ.....97..580T, doi:10.1086/115007.
    5. Schmadel, Lutz D. (2003), Dictionary of Minor Planet Names, 1 (5th ed.), Springer, p. 26, ISBN 3540002383.
    6. Dunham, D. W.; et al. (September 2002), "Asteroidal occultation results multiply helped by Hipparcos", The Minor Planet Bulletin, 73 (3), p. 662, Bibcode:2002MmSAI..73..662D.
    7. "JPL Small-Body Database Search Engine: diameter > 150 (km) and rot_per > 24 (h)". JPL Solar System Dynamics. Retrieved June 6, 2015.


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