Scientific and educational institution or venue for popularizing astronomical knowledge, typically equipped with tools like planetarium projectors and telescopes.

The scientific study of stars, planets, and other objects in space.

enormous figure or sky-high number (originally referring to numbers used in astronomy to represent distances between celestial bodies)

astronomical observatory; institution equipped for the study of celestial objects and phenomena

A telescope used for observing celestial bodies and astronomical phenomena; includes optical, reflecting, and refracting types

Purple Mountain Observatory; a major astronomical research institute located in Nanjing, China

astronomical unit (AU); a unit of distance used in astronomy equal to the average distance between the Earth and the Sun, approximately 150 million kilometers

An astronomical clock or high-precision chronometer used for determining exact time, often kept under vacuum at a constant temperature.

Mean solar time calculated from one noon to the next in a continuous twenty-four hour cycle, without dividing the day into a.m. and p.m.

The Almagest, a 2nd-century mathematical and astronomical treatise on the motions of the stars and planetary paths, written by the Greek scholar Ptolemy

A branch of astronomy that studies celestial bodies and phenomena by observing the radio waves they emit; it uses electromagnetic radiation like radio and light waves to explore the universe

an optical instrument used for observing celestial objects and distant stars

a time interval measured by the rotation of the Earth relative to a celestial body or point, such as the sun or a star