Astronomy:128 Nemesis

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128 Nemesis
Discovery[1]
Discovered byJames Craig Watson
Discovery date25 November 1872
Designations
(128) Nemesis
Pronunciation/ˈnɛmɪsɪs/[3]
Named afterNemesis
A872 WA; 1952 HW1
Minor planet categorymain-belt[1][2] · Nemesis
AdjectivesNemesian /nəˈmiːʒ(i)ən/[4][5]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc144.93 yr (52,934 d)
|{{{apsis}}}|helion}}3.10 astronomical unit|AU (463.69 Gm)
|{{{apsis}}}|helion}}2.40 AU (359.00 Gm)
2.75 AU (411.35 Gm)
Eccentricity0.1272
Orbital period4.56 years (1,665 d)
Mean anomaly345.49°
Mean motion0° 12m 58.32s / day
Inclination6.2453°
Longitude of ascending node76.243°
303.82°
Physical characteristics
Mean diameter163±5 km[6]
162.5±1.3 km[7]
184.2±5.2 km[8]
Flattening0.17[lower-alpha 1]
Mass(3.4±1.7)×1018 kg[6]
(6.0±2.6)×1018 kg[8]
Mean density1.5±0.8 g/cm3[6]
1.82±0.79 g/cm3[8]
Rotation period77.81 h (3.242 d)[9]
38.9325 h (1.62219 d)[2]
Geometric albedo0.067 (calculated)[6]
0.067±0.005[2]
Tholen = C[2]
SMASS = C[2]
Absolute magnitude (H)7.70[2]


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.[2][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,[2] and named after Nemesis, the goddess of retribution in Greek mythology.

Diagram of Nemesis's orbit

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, Nemesis has been observed to occult eight stars.

Notes

  1. ↑ Flattening derived from the maximum aspect ratio (c/a): f=1−ca, where (c/a) = 0.83±0.04.[6]

References

  1. ↑ 1.0 1.1 "128 Nemesis". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=128. Retrieved 14 September 2018. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 "JPL Small-Body Database Browser: 128 Nemesis". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000128. Retrieved 14 September 2018. 
  3. ↑ Nemesis (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=Nemesis  (Subscription or UK public library membership required.)
  4. ↑ Hornum (1993) Nemesis, the Roman state and the games
  5. ↑ Peery (1963) Studies in the Renaissance, vol. 10
  6. ↑ 6.0 6.1 6.2 6.3 6.4 P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
  7. ↑ 7.0 7.1 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. doi:10.1088/0004-637X/791/2/121. Bibcode: 2014ApJ...791..121M. 
  8. ↑ 8.0 8.1 8.2 Carry, B. (December 2012), "Density of asteroids", Planetary and Space Science 73 (1): 98–118, doi:10.1016/j.pss.2012.03.009, Bibcode: 2012P&SS...73...98C.  See Table 1.
  9. ↑ 9.0 9.1 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, doi:10.1016/0019-1035(79)90121-0, Bibcode: 1979Icar...37..133S. 
  10. ↑ DeMeo, Francesca E. et al. (July 2009), "An extension of the Bus asteroid taxonomy into the near-infrared", Icarus 202 (1): 160–180, doi:10.1016/j.icarus.2009.02.005, Bibcode: 2009Icar..202..160D, archived from the original on 2014-03-17, https://web.archive.org/web/20140317200310/https://www.tara.tcd.ie/bitstream/2262/43276/1/PEER_stage2_10.1016/j.icarus.2009.02.005.pdf, retrieved 2013-04-08.  See appendix A.
  11. ↑ "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. http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all;obj_kind=ast;obj_numbered=all;ast_orbit_class=IMB;ast_orbit_class=MBA;ast_orbit_class=OMB;OBJ_field=0;ORB_field=0;c1_group=OBJ;c1_item=Ap;c1_op=%3E;c1_value=188.1;table_format=HTML;max_rows=500;format_option=comp;c_fields=AcApAiBhBgBjBkBlBiBnBs;.cgifields=format_option;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=com_orbit_class&query=1&c_sort=ApA. Retrieved 2012-04-17. 
  12. ↑ 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. 
  13. ↑ "JPL Small-Body Database Search Engine: diameter > 150 (km) and rot_per > 24 (h)". JPL Solar System Dynamics. http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all;obj_kind=all;obj_numbered=all;OBJ_field=0;ORB_field=0;combine_mode=AND;c1_group=OBJ;c1_item=Ap;c1_op=%3E;c1_value=150;c2_group=OBJ;c2_item=As;c2_op=%3E;c2_value=24;table_format=HTML;max_rows=50;format_option=comp;c_fields=AcBhBgBjBiBnBsAiApAs;.cgifields=format_option;.cgifields=ast_orbit_class;.cgifields=combine_mode;.cgifields=table_format;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=com_orbit_class&query=1&c_sort=AsD. Retrieved 2015-06-06. 



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