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Register a new userAnalysis of the Karma asteroid family
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Authors
Debora Pavela
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The Karma asteroid family is a group of primitive asteroids in the middle part of the main belt, just at the outer edge of the 3J:1A mean-motion resonance. We obtained the list of the family members with 317 asteroids and estimated that it was formed by the catastrophic disruption of a parent body that was between 34 and 41 km in diameter. Based on the V-shape method, age of the Karma family is estimated to be about 137 Myr. A detailed dynamical map of the region combined with numerical simulations allowed us to reconstruct the long-term dynamical evolution of the family, and to identify the mechanisms responsible for this evolution. The numerical simulations successfully reproduced the main features in the orbital distribution of the family members but also showed that some regions of the Karma family could be missing. A more detailed analysis revealed that these regions likely consist of very dark objects, fainter than absolute magnitude H = 17, that have not yet been detected. Based on the obtained results, we concluded that magnitude-frequency distribution of family members up to H = 16 mag is neither affected by dynamical erosion nor observational incompleteness and therefore represents the result of collisional grinding of the original family population. Finally, we found that the Karma family have been supplying some asteroids to the near-Earth region via the 3J:1A resonance. Currently, there should about 10 family members larger than 1 km in diameter, orbiting in the near-Earth space.
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We report on the results of a systematic search for associated asteroid families for all active asteroids known to date. We find that 10 out of 12 main-belt comets (MBCs) and 5 out of 7 disrupted asteroids are linked with known or candidate families, rates that have ~0.1% and ~6% probabilities, respectively, of occurring by chance, given an overall family association rate of 37% for asteroids in the inner solar system. We find previously unidentified family associations between 238P/Read and the candidate Gorchakov family, 311P/PANSTARRS and the candidate Behrens family, 324P/La Sagra and the Alauda family, 354P/LINEAR and the Baptistina family, P/2013 R3-B (Catalina-PANSTARRS) and the Mandragora family, P/2015 X6 (PANSTARRS) and the Aeolia family, P/2016 G1 (PANSTARRS) and the Adeona family, and P/2016 J1-A/B (PANSTARRS) and the Theobalda family. All MBCs with family associations belong to families that contain asteroids with primitive taxonomic classifications and low average reported albedos (pV_avg < 0.10), while disrupted asteroids with family associations belong to families that contain asteroids that span wider ranges of taxonomic types and average reported albedos (0.06 < pV_avg < 0.25). These findings are consistent with MBC activity being closely correlated to composition (i.e., whether an object is likely to contain ice), while disrupted asteroid activity is not as sensitive to composition. Given our results, we describe a sequence of processes by which the formation of young asteroid families could lead to the production of present-day MBCs.
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