HELIACAL, a term applied to a star or planet, with reference either to its emergence from the light of the sun, or immersion into it. A star is said to rise heliacally when, after being in conjunction with the sun, it gets at such a
distance from it as to become visible before sun-rising. The heliacal setting of a star denotes its entering into the sun's rays, and thus becoming lost in the superior splendour of that luminary.