  Asymmetric debris discs have been found around stars other than the Sun;
asymmetries are sometimes attributed to perturbations induced by unseen
planets. The presence or absence of asymmetries in our own trans-Neptunian belt
remains controversial. The study of sensitive tracers in a sample of objects
relatively free from the perturbations exerted by the four known giant planets
and most stellar flybys may put an end to this debate. The analysis of the
distribution of the mutual nodal distances of the known extreme trans-Neptunian
objects (ETNOs) that measure how close two orbits may get to each other could
be such a game changer. Here, we use a sample of 51 ETNOs together with random
shufflings of this sample and two unbiased scattered-disc orbital models to
confirm a statistically significant (62 sigma) asymmetry between the shortest
mutual ascending and descending nodal distances as well as the existence of
multiple highly improbably (p < 0.0002) correlated pairs of orbits with mutual
nodal distances as low as 0.2 au at 152 au from the Solar system's barycentre
or 1.3 au at 339 au. We conclude that these findings fit best with the notion
that trans-Plutonian planets exist.

Earth and Planetary Astrophysics