128 Nemesis

Nemesis (minor planet designation: 128 Nemesis) is a large 180 km main-belt asteroid, of carbonaceous composition. It rotates rather slowly, taking about 78 hours to complete one rotation.[3][8] Nemesis is the largest member of the Nemesian asteroid family bearing its name. It was discovered by J. C. Watson on 25 November 1872,[3] and named after Nemesis, the goddess of retribution in Greek mythology. Nemesis was also the name of a hypothetical companion star of the Sun, which does not exist.

128 Nemesis
Discovery[1]
Discovered byJames Craig Watson
Discovery date25 November 1872
Designations
(128) Nemesis
Pronunciation/ˈnɛmɪsɪs/[2]
Named after
Nemesis
main-belt [1][3] · Nemesis
AdjectivesNemesian /nəˈmiːʒ(i)ən/[4][5]
Orbital characteristics [3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc144.93 yr (52,934 d)
Aphelion3.10 AU (463.69 Gm)
Perihelion2.40 AU (359.00 Gm)
2.75 AU (411.35 Gm)
Eccentricity0.1272
4.56 years (1,665 d)
345.49°
0° 12m 58.32s / day
Inclination6.2453°
76.243°
303.82°
Physical characteristics
Mean diameter
162.515±1.296 km[6]
184.19 ± 5.19 km[7]
Mass(5.97±2.56)×1018 kg[7]
Mean density
1.82±0.79 g/cm3[7]
77.81 h (3.242 d)[3]
0.0504±0.002[3]
Tholen = C [3]
SMASS = C [3]
7.49[3]

    This object is orbiting the Sun with a period of 4.56 years and an eccentricity (ovalness) of 0.13. The orbital plane is inclined by 6.2° to the plane of the ecliptic. It is categorized as a C-type asteroid,[9] indicating a primitive carbonaceous composition. Based on IRAS data Nemesis is about 188 km in diameter and is around the 33rd largest main-belt asteroid,[10] while WISE measurements yield a size of ~163 km.[6] The 77.81‑hour[11] rotation period is the second longest for an asteroid more than 150 km in diameter.[12]

    References
    1. "128 Nemesis". Minor Planet Center. Retrieved 14 September 2018.
    2. "Nemesis". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
    3. "JPL Small-Body Database Browser: 128 Nemesis" (2017-10-31 last obs.). Jet Propulsion Laboratory. Retrieved 14 September 2018.
    4. Hornum (1993) Nemesis, the Roman state and the games
    5. Peery (1963) Studies in the Renaissance, vol. 10
    6. Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121.
    7. Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science, 73 (1): 98–118, arXiv:1203.4336, Bibcode:2012P&SS...73...98C, doi:10.1016/j.pss.2012.03.009. See Table 1.
    8. Scaltriti, F.; Zappala, V.; Schober, H. J. (January 1979), "The rotations of 128 Nemesis and 393 Lampetia - The longest known periods to date", Icarus, 37 (1): 133–141, Bibcode:1979Icar...37..133S, doi:10.1016/0019-1035(79)90121-0.
    9. DeMeo, Francesca E.; et al. (July 2009), "An extension of the Bus asteroid taxonomy into the near-infrared" (PDF), Icarus, 202 (1): 160–180, Bibcode:2009Icar..202..160D, doi:10.1016/j.icarus.2009.02.005, archived from the original (PDF) on 17 March 2014, retrieved 8 April 2013. See appendix A.
    10. "JPL Small-Body Database Search Engine: asteroids and orbital class (IMB or MBA or OMB) and diameter > 188.1 (km)". JPL's Solar System Dynamics Group. Retrieved 17 April 2012.
    11. Pilcher, Frederick (July 2015), "New Photometric Observations of 128 Nemisis [sic], 249 Ilse, and 279 Thule", The Minor Planet Bulletin, 42 (3): 190−192, Bibcode:2015MPBu...42..190P.
    12. "JPL Small-Body Database Search Engine: diameter > 150 (km) and rot_per > 24 (h)". JPL Solar System Dynamics. Retrieved 6 June 2015.


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