For questions related to planets, moons, stars and other celestial objects, and their motion on the sky.
Astronomy is often considered a subset of physics, although it may be a branch of science in its own right. The prefix "astro-" literally translates as "star", but astronomy ventures into the investigation of many other different celestial objects. Consider using more specialized tags with the astronomy tag, such as planets and stars if the question deals with one of these objects, or space if your questions deals with activities in outer space. Other tags, such as astrophysics and orbital-mechanics may also be useful.