A beam of light, through special optical devices such as prisms and gratings, can be decomposed into a series of light of different wavelengths. The pattern formed by them is called a spectrum. The most common spectrum in nature is the rainbow after a rainstorm. The first person to carefully observe and analyze the spectrum was Newton, who obtained the solar spectrum using a prism. Later, physicists and astronomers began to conduct extensive classification and research on the solar spectrum and stellar spectra, gaining some basic knowledge of the spectrum. A specific line in the spectrum, called a spectral line, is produced at a specific position in the spectrum. The nature of the spectral lines is related to the elements contained in the celestial body and their abundance and ionization state. Based on this clue, astronomers gradually learned about the elements that make up these stars by studying the stellar spectra and determined their composition ratios.
As humans gained a deeper understanding of the classification of spectra and stellar atmospheric models, the role of spectra was not just used to identify the elemental composition of stellar atmospheres, but also to study the structure and evolution of stars. By the 1960s, with the widespread application of computers, scientists gained a more detailed understanding of the radiation mechanisms of astrophysics. Astronomers compared the actual observed spectra with those calculated by various radiation models to infer the information behind the spectra. For example, by analyzing the spectra of supernova remnants, we can determine the stage of evolution of the supernova remnant; by studying the infrared spectra of protostellar systems, we can speculate on the growth stage of protostars and study how stars are born.
Obtaining the spectra of celestial bodies is called spectroscopy in astronomy. With the increasing aperture of telescopes and the advancement of spectroscopic equipment, astronomers can now conduct spectroscopic observations in all wavelengths from radio, infrared, and visible light to high-energy gamma rays. The resulting spectra will reveal more mysteries of the universe to us.