2003EL61 and Varuna are believed to be in hydrostatic equilibrium AND triaxial ellipsoids.<br />See link for 2003EL61:<br />http://www.gps.caltech.edu/~mbrown/2003EL61/<br /><br />I have tried desperately several combinations of rock and ice, of course taking into account the centrifugal force due to the very fast spin assumed for 2003el61. But I cannot succeed in generating an equilibrium for 2003el61. For a biaxial ellipsoid, yes of course. But not a 3D one. <br />The dimensions are thought to be (based on lightcurves):<br />2003EL61: b/a = 0.77, c/a = 0.5<br />Varuna: b/a = 0.63 âˆ’ 0.80, c/a = 0.45 âˆ’ 0.52 <br /><br />c/a value is consistent with fast spin (classical flattening at poles, quite extreme there)<br />But I cannot make sense of such low values for b/a <br /><br />I am really wondering whether thay have not missed something in the lightcurve, (e.g. two spots with double dip of an object rotating twice slower than expected) or a very close binary.<br /><br />May be Varuna is not in hydrostatic equilibirum after all.<br />But for 2003EL61, it is difficult to believe that such a big object, with such a density (hence large rocky material = /> radiogenic heat), and a collisional record (member of a collisional family) is not differentiated. That means hydrostatic equilibirum. But then how can b/a be so low????<br /><br />Any clue for having a body in equilibrium with an elliptical equator b/a of 0.8?