Astronomical spectroscopy is a technique used by astronomers to study the light emitted or absorbed by celestial objects. By analyzing the spectrum of light, which is the range of colors produced when light is separated, scientists can determine the composition, temperature, density, and motion of stars and galaxies. This method involves using instruments called spectrometers to break down light into its component colors, revealing unique patterns known as spectral lines. Each element emits or absorbs light at specific wavelengths, allowing astronomers to identify the chemical makeup of distant objects and gain insights into the universe's structure and evolution.