aphelion – the point in the orbit of a planet, asteroid, or comet at which it is farthest from the Sun. astral – relating to or resembling the stars. caldera – a large volcanic crater, especially one formed by a major eruption leading to the collapse of the mouth of the volcano. celestial – positioned in or relating to the sky, or outer space as observed in astronomy. constellation – a group of stars forming a recognizable pattern. cosmos – the universe seen as a well-ordered whole. equinox – the time or date at which the sun crosses the celestial equator, when day and night are of equal length. faculae – bright patches that are visible on the Sun’s surface. lunation – the interval of a complete lunar cycle, between one new Moon and the next. interstellar – occurring or situated between stars. nebula – a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter. perihelion – the point in the orbit of a planet, asteroid, or comet at which it is closest to the Sun. synodic – relating to or involving the conjunction of stars, planets, or other celestial objects.