Planets that orbit at very related distances from their stars could jockey for place whereas nonetheless remaining in a broadly steady configuration for billions of years – lengthy sufficient to be noticed by astronomers. Such star programs would possibly be so unlikely that they could solely be created artificially, by advanced alien civilisations.
Most planets have their orbits to themselves, however orbital mechanics permits for worlds to be shut sufficient to successfully share an orbit, forcing them into a helter-skelter dance the place they …