While satellites of mid- to small-Kuiper belt objects tend to be similar in
size and brightness to their primaries, the largest Kuiper belt objects
preferentially have satellites with small fractional brightness. In the two
cases where the sizes and albedos of the small faint satellites have been
measured, these satellites are seen to be small icy fragments consistent with
collisional formation. Here we examine Dysnomia and Vanth, the satellites of
Eris and Orcus, respectively. Using the Atacama Large Millimeter Array, we
obtain the first spatially resolved observations of these systems at thermal
wavelengths. We find a diameter for Dysnomia of 700+/-115 km and for Vanth of
475+/-75 km, with albedos of 0.04_+0.02_-0.01 and 0.08+/-0.02 respectively.
Both Dysnomia and Vanth are indistinguishable from typical Kuiper belt objects
of their size. Potential implications for the formation of these types of
satellites are discussed.Comment: AJ, in pres
