Spin vector alignment of Koronis family asteroids


Studies of asteroid families—groups of asteroids that formed from the fragmentation of larger bodies—are of broad interest to solar system researchers because they can provide insights into collisional processes, as well as the interior structures, strengths, and compositions of asteroids. It is generally accepted that members of the Koronis family were created by collisional disruption of a homogeneous parent body1 and therefore share the same formation age and subsequent collisional history. The temporal variations in observed brightnesses of the Koronis family members (a consequence of their rotation) are, however, larger than expected2. Preferential alignment of spin vectors had been proposed2 as a possible explanation, but recent modelling3 predicted that family formation yields random spin vectors among the resulting fragments. Both hypotheses have been untested by observations. Here I show that the actual distribution of spin vectors among the largest members of the Koronis family falls within markedly nonrandom ‘spin clusters’. Reconciling models of family formation and evolution with the unexpected alignments of spin obliquities and correlations with spin rates presents a new challenge in understanding asteroid collisional processes.

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Figure 1: Light curves of (311) Claudia showing the doubly periodic change in brightness as it rotates once in 7.531 h.
Figure 2: Effect of changing illumination geometry on the observed mean brightness of (158) Koronis during a 36-day interval in 1994.
Figure 3: Spin angular momentum in the Koronis family of asteroids.


  1. 1

    Chapman, C. R., Paolicchi, P., Zappalà, V., Binzel, R. P. & Bell, J. F. in Asteroids II (eds Binzel, R. P., Gehrels, T. & Matthews, M. S.) 386–415 (Univ. Arizona Press, Tucson, 1989)

    Google Scholar 

  2. 2

    Binzel, R. P. Collisional evolution in the Eos and Koronis asteroid families: Observational and numerical results. Icarus 73, 303–313 (1988)

    ADS  Article  Google Scholar 

  3. 3

    Michel, P., Benz, W., Tanga, P. & Richardson, D. C. Collisions and gravitational reaccumulation: Forming asteroid families and satellites. Science 294, 1696–1700 (2001)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Zappalà, V., Bendjoya, Ph., Cellino, A., Farinella, P. & Froeschle, C. Asteroid families: Search of a 12,487-asteroid sample using two different clustering techniques. Icarus 116, 291–314 (1995)

    ADS  Article  Google Scholar 

  5. 5

    Binzel, R. P. A photoelectric survey of 130 asteroids. Icarus 72, 135–208 (1987)

    ADS  Article  Google Scholar 

  6. 6

    Slivan, S. M. Spin-Axis Alignment of Koronis Family Asteroids PhD thesis, Massachusetts Institute of Technology (1995)

    Google Scholar 

  7. 7

    Slivan, S. M. & Binzel, R. P. Forty-eight new rotation lightcurves of 12 Koronis family asteroids. Icarus 124, 452–470 (1996)

    ADS  Article  Google Scholar 

  8. 8

    Slivan, S. M. et al. Spin vectors in the Koronis family: Comprehensive results from two independent analyses of 213 rotation lightcurves. Icarus (submitted).

  9. 9

    Drummond, J. D., Weidenschilling, S. J., Chapman, C. R. & Davis, D. R. Photometric geodesy of main-belt asteroids. II. Analysis of lightcurves for poles, periods, and shapes. Icarus 76, 19–77 (1988)

    ADS  Article  Google Scholar 

  10. 10

    Kaasalainen, M. & Torppa, J. Optimization methods for asteroid lightcurve inversion. I. Shape determination. Icarus 153, 24–36 (2001)

    ADS  Article  Google Scholar 

  11. 11

    Kaasalainen, M., Torppa, J. & Muinonen, K. Optimization methods for asteroid lightcurve inversion. II. The complete inverse problem. Icarus 153, 37–51 (2001)

    ADS  Article  Google Scholar 

  12. 12

    Binzel, R. P. et al. Asteroid 243 Ida: Ground-based photometry and a pre-Galileo physical model. Icarus 105, 310–325 (1993)

    ADS  Article  Google Scholar 

  13. 13

    Davies, M. E. et al. The north pole direction and the control network of the asteroid 243 Ida. Bull. Am. Astron. Soc. 26, 1154–1155 (1994)

    ADS  Google Scholar 

  14. 14

    Miller, I. & Freund, J. E. Probability and Statistics for Engineers (Prentice-Hall, Englewood Cliffs, New Jersey, 1977)

    Google Scholar 

  15. 15

    Belton, M. J. S. et al. First images of asteroid 243 Ida. Science 265, 1543–1547 (1994)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Marzari, F., Davis, D. & Vanzani, V. Collisional evolution of asteroid families. Icarus 113, 168–187 (1995)

    ADS  Article  Google Scholar 

  17. 17

    Rubincam, D. P. Radiative spin-up and spin-down of small asteroids. Icarus 148, 2–11 (2000)

    ADS  Article  Google Scholar 

  18. 18

    Bowell, E., et al. in Asteroids II (eds Binzel, R. P., Gehrels, T. & Matthews, M. S.) 524–556 (Univ. Arizona Press, Tucson, 1989)

    Google Scholar 

  19. 19

    Landolt, A. U. UVBRI photometric standard stars around the celestial equator. Astron. J. 88, 439–460 (1983)

    ADS  Article  Google Scholar 

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I thank R. Binzel for advice and encouragement, and M. Kaasalainen, L. Crespo da Silva, M. Lyndaker and M. Krc̆o for contributions at various stages of this work.

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Correspondence to Stephen M. Slivan.

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Slivan, S. Spin vector alignment of Koronis family asteroids. Nature 419, 49–51 (2002). https://doi.org/10.1038/nature00993

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