ecliptic

Conjunctions occur frequently in our solar system because "the planets orbit around the Sun in approximately the same plane - the ecliptic plane - and thus trace similar paths across our sky", according to Nasa.

Because we’re in that plane, we see it edge on as a line across the sky called the ecliptic.

That trajectory eventually took Voyager 1 “north” and out of the ecliptic—the plane of the solar system.

Babylonian astronomers had previously measured the positions of some stars around the zodiac, the constellations that lie along the ecliptic—the Sun’s annual path against the fixed stars, as seen from Earth.

Space physicists later worked out that models had largely ignored interstellar magnetic fields, which compress the heliosphere below the ecliptic, Provornikova says.