The arcing line joining the planets defines the arc of the ecliptic.
A panorama showing the Milky Way (centre) and planets. Mars is bright to the left, Saturn is dimmer and bright Jupiter is right. The arcing line joining the planets defines the arc of the ecliptic. Credit: Alan Dyer / Stocktrek Images / Getty ImagesA panorama showing the Milky Way (centre) and planets. Mars is bright to the left, Saturn is dimmer and bright Jupiter is right. The arcing line joining the planets defines the arc of the ecliptic. Credit: Alan Dyer / Stocktrek Images / Getty Images