The first dissenter and the first contact: what the onset of disruption reveals about the ejected body

We examine whether the onset of the disruption of a three-body system reveals which body will be ejected. Starting from the perturbed Lagrange triangle, we define the first dissenter in four ways and find, in 4,400 regularized planar integrations, that it does not predict the ejected body: with equal masses, the success rate lies between 29% and 40%, at the level of chance, because 105 to 135 close encounters occur between the onset and the ejection; with unequal masses, the apparent signal is an effect of the mass. We then test, in 30,000 integrations with masses 1, 1, and q (q from 2 to 30) and three types of start, whether the light mass that first forms a close pair with the heavy one remains with it. In the symmetric start, this occurs in 64% to 83% of cases, with an advantage that grows with q, whereas initial proximity predicts nothing. In random starts, the effect falls to 54% to 61% and is largely confounded with the advantage of starting closer. An energy decomposition, in 18,000 additional integrations, shows the origin of the effect: when the first contact pair already holds more binding than the total energy of the system, the other light mass is expelled in the encounter itself and the light mass of the contact remains in 91% to 100% of cases; outside these cases, the effect is smaller and grows with the binding of the pair.