Predict the eventual advance of the currently active inner hotspot

Determine how far the currently active inner hotspot in a multi-episode radio galaxy will ultimately advance beyond the older hotspots.

Background

The paper notes that the inner hotspot is presumably still being energized by an active jet, whereas the more distant hotspots are inactive relics from earlier episodes. The authors explain that the available comparison cannot establish whether an outer hotspot might eventually be overtaken by a younger active hotspot because the future propagation of the currently active inner hotspot is unknown.

This uncertainty is identified as a limitation that can only be addressed definitively using sources with at least two non-active hotspots, corresponding to radio galaxies with three or more episodes of jet activity.