An equinox is commonly regarded as the instant of time when the plane of Earth's equator passes through the center of the Sun. This occurs twice each year: around 20 March and 23 September. In other words, it is the moment at which the center of the visible Sun is directly above the Equator.
What is the name for the branch of astronomy that relates to precise measurements and explanations of the positions and movements of celestial bodies?
In astronomy, what is the word applied to the alignment of three or more celestial bodies in the same gravitational system along a straight line?
What device, a tool for studying astronomical phenomena, uses the fact that when a material is heated to incandescence it emits light that is characteristic of the atomic makeup of the material?