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128 Nemesis
Discovery
Discovered by	James Craig Watson
Discovery date	25 November 1872
Designations
MPC designation	(128) Nemesis
Pronunciation	/ˈnɛmɪsɪs/
Named after	Nemesis
Alternative designations	A872 WA; 1952 HW1
Minor planet category	main-belt · Nemesis
Adjectives	Nemesian /nəˈmiːʒ(i)ən/
Orbital characteristics
	Epoch 23 March 2018 (JD 2458200.5)
	Uncertainty parameter 0
Observation arc	144.93 yr (52,934 d)
Aphelion	3.10 AU (463.69 Gm)
Perihelion	2.40 AU (359.00 Gm)
Semi-major axis	2.75 AU (411.35 Gm)
Eccentricity	0.1272
Orbital period (sidereal)	4.56 years (1,665 d)
Mean anomaly	345.49°
Mean motion	0° 12m 58.32s / day
Inclination	6.2453°
Longitude of ascending node	76.243°
Argument of perihelion	303.82°
Physical characteristics
Mean diameter	163±5 km; 162.5±1.3 km; 184.2±5.2 km
Flattening	0.17
Mass	(3.4±1.7)×1018 kg ; (6.0±2.6)×1018 kg
Mean density	1.5±0.8 g/cm3; 1.82±0.79 g/cm3
Synodic rotation period	77.81 h (3.242 d); 38.9325 h (1.62219 d)
Geometric albedo	0.067 (calculated); 0.067±0.005
Spectral type	Tholen = C; SMASS = C
Absolute magnitude (H)	7.70

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]^[9] 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.

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,^[10] 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,^[11] while WISE measurements yield a size of ~163 km.^[7] The 77.81‑hour^[12] rotation period is the second longest for an asteroid more than 150 km in diameter.^[13]

Between 2005 and 2021, 128 Nemesis has been observed to occult eight stars.

Notes

^ Flattening derived from the maximum aspect ratio (c/a): $f=1-{\frac {c}{a}}$ , where (c/a) = 0.83±0.04.^[6]

References

^ ^a ^b "128 Nemesis". Minor Planet Center. Retrieved 14 September 2018.
^ "Nemesis". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ "JPL Small-Body Database Browser: 128 Nemesis" (2017-10-31 last obs.). Jet Propulsion Laboratory. Retrieved 14 September 2018.
^ Hornum (1993) Nemesis, the Roman state and the games
^ Peery (1963) Studies in the Renaissance, vol. 10
^ ^a ^b ^c ^d ^e P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
^ ^a ^b 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. S2CID 119293330.
^ ^a ^b ^c 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, S2CID 119226456. See Table 1.
^ ^a ^b 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.
^ 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.
^ "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.
^ 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.
^ "JPL Small-Body Database Search Engine: diameter > 150 (km) and rot_per > 24 (h)". JPL Solar System Dynamics. Retrieved 6 June 2015.

External links

128 Nemesis at AstDyS-2, Asteroids—Dynamic Site
- Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
128 Nemesis at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters
Nemesis found! (2013) on YouTube

[9] Flattening derived from the maximum aspect ratio (c/a): $f=1-{\frac {c}{a}}$ , where (c/a) = 0.83±0.04.^[6]

[MPC-object-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.)

[jpldata-3] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ "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

[VLT-6] P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56

[Masiero-2014-7] 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. S2CID 119293330.

[Carry2012-8] 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, S2CID 119226456. See Table 1.

[Scaltriti1979-10] 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.

[DeMeo2009-11] 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.

[jpl-search-12] "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.

[Pilcher2015-13] 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.

[SBDB-14] "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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