Component size ratio (D_s/D_p) is secondary diameter divided by primary diameter. Symbol sizes indicate component separation (a/R_p) expressed in terms of the radius of the primary. Some values are estimated based on assumed albedoes, densities, etc.

Binary dynamical types are based on taxonomy described by Pravec and Harris (2007) and by Lindsay et al. (2014); more discussion is available here. In summary, type codes are:

• A = small binary (D_p<20 km) with smaller secondary (D_s/D_p<0.5)
• B = small binary (D_p<20 km) with similar sized secondary (D_s/D_p>0.8)
• C = contact binary
• L = large asteroid (D_p>90 km) with small satellite (D_s/D_p<0.25)
• O = outlier, particularly large asteroid (D_p>90 km) with similar sized secondary (D_s/D_p>0.8)
• U = unclassified
• W = wide small binary (D_p<10 km, A₂/D_p>10)

• For main belt and near-Earth asteroids, distinct dynamical types are evident and described in the above references.
• Many of the A type systems are understood to represent components formed from mass shedding during YORP-driven rotational spinup.
• A continuous range of characteristics is seen for the TNO population, including systems with very large separations, stable by virtue of the systems' large distances from the Sun and planets. Note that detection biases introduce cutoffs in known TNO systems, illustrated by the line for constant secondary component size (D₂ = 60 km).

References:

• Lindsay, S. S., F. Marchis, J. P. Emery, J. E. Enriquez, and M. Assafin, 2014, Composition, mineralogy, and porosity of multiple asteroid systems from visible and near-infrared spectral data, ArXiv, 1409.0359.
• Pravec, P., and A. W. Harris, 2007, Binary asteroid population I. Angular momentum content, Icarus, 190:250-259.

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© 2014-2019, 2021 by Wm. Robert Johnston.
Last modified 13 October 2021.
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