8991 Solidarity

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8991 Solidarity
Discovery [1]
Discovered by La Silla Obs.
Discovery site La Silla, Chile
Discovery date 6 August 1980
MPC designation (8991) Solidarity
Named after
(in memory of 9/11)[2]
1980 PV1 · 1975 QB
1979 HC1 · 1985 SD3
1988 FR3 · 1988 GW2
main-belt · (middle)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 41.57 yr (15,183 days)
Aphelion 3.2956 AU
Perihelion 2.2799 AU
2.7877 AU
Eccentricity 0.1822
4.65 yr (1,700 days)
0° 12m 42.48s / day
Inclination 6.7882°
Physical characteristics
Dimensions 8.385±0.342 km[4][5]
12.88 km (calculated)[3]
5.2388±0.0034 h[6]
0.057 (assumed)[3]
12.37±1.03[7] · 12.729±0.003 (R)[6] · 12.8[1] · 12.9[4] · 13.18[3]

8991 Solidarity, provisional designation 1980 PV1, is a carbonaceous asteroid from the middle region of the asteroid belt, approximately 10 kilometers in diameter. It was discovered on 6 August 1980, by observers at ESO's La Silla Observatory site in northern Chile.[8] The asteroid was named in response to the September 11 attacks.[2]

Orbit and classification[edit]

Solidarity orbits the Sun in the central main-belt at a distance of 2.3–3.3 AU once every 4 years and 8 months (1,700 days). Its orbit has an eccentricity of 0.18 and an inclination of 7° with respect to the ecliptic.[1] The first used observation was made at Cerro El Roble Observatory in 1979, extending the body's observation arc by 1 year prior to its official discovery observation at La Silla.[8]

Physical characteristics[edit]

Rotation period[edit]

In January 2011, a rotational lightcurve of Solidarity was obtained from photometric observations at the Palomar Transient Factory in California. It gave a rotation period of 5.2388 hours with a brightness variation of 0.19 magnitude (U=2).[6]

Diameter and albedo[edit]

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Solidarity measures 8.4 kilometers in diameter and its surface has an albedo of 0.17,[4][5] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 12.9 kilometers with an absolute magnitude of 13.18.[3]


This minor planet was named "Solidarity" in response to the September 11 attacks. As a commemorative gesture, the IAU's Committee for the Nomenclature of Small Bodies chose three objects discovered in observatories on different continents and christened them with names representing some of the most basic and universal human values. The other two selections were 8990 Compassion (discovered from Europe) and 8992 Magnanimity (discovered from Asia).[2] The official naming citation was published by the Minor Planet Center on 2 October 2001 (M.P.C. 43684).[9]


  1. ^ a b c d "JPL Small-Body Database Browser: 8991 Solidarity (1980 PV1)" (2017-03-11 last obs.). Jet Propulsion Laboratory. Retrieved 22 June 2017. 
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (8991) Solidarity. Springer Berlin Heidelberg. p. 674. ISBN 978-3-540-00238-3. Retrieved 10 July 2016. 
  3. ^ a b c d e f "LCDB Data for (8991) Solidarity". Asteroid Lightcurve Database (LCDB). Retrieved 10 July 2016. 
  4. ^ a b c d Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. Bibcode:2011ApJ...741...90M. arXiv:1109.6407Freely accessible. doi:10.1088/0004-637X/741/2/90. Retrieved 10 July 2016. 
  5. ^ a b c Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. Bibcode:2011ApJ...741...68M. arXiv:1109.4096Freely accessible. doi:10.1088/0004-637X/741/2/68. Retrieved 4 December 2016. 
  6. ^ a b c Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry". The Astronomical Journal. 150 (3): 35. Bibcode:2015AJ....150...75W. arXiv:1504.04041Freely accessible. doi:10.1088/0004-6256/150/3/75. Retrieved 10 July 2016. 
  7. ^ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. Bibcode:2015Icar..261...34V. arXiv:1506.00762Freely accessible. doi:10.1016/j.icarus.2015.08.007. Retrieved 10 July 2016. 
  8. ^ a b "8991 Solidarity (1980 PV1)". Minor Planet Center. Retrieved 10 July 2016. 
  9. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 10 July 2016. 

External links[edit]