In spectroscopic observations, electromagnetic radiation from an astronomical object is collected and analyzed to obtain information about that object’s physical properties. The most common type of spectroscopy used in astronomy is optical spectroscopy, which observes visible light from objects. However, other types of spectroscopy can be used to observe different types of electromagnetic radiation, such as ultraviolet light, X-rays, and gamma rays.
The study of spectra has a long history in astronomy. In the 19th century, astronomers began using spectroscopes to classify stars according to their spectral lines. This led to the discovery of stellar classification schemes such as the Harvard classification system. In the early 20th century, astronomers usedspectrographs to measure the radial velocities of stars; this allowed for the determination of stellar orbits and the masses of binary star systems.
With the development of space-based telescopes and instrumentation, spectroscopic observations have become increasingly important in modern astronomy. For example, data from the ultraviolet spectrum can be used to study hot gas in galaxies or accreting black holes. Optical data can be used to study star formation or planetary atmospheres. And infrared data can be used to study cooler gas and dust around protostars or exoplanets.
There are many different types of spectroscopic observations that can be made depending on what physical quantity one wishes to measure. For example, line ratios can be measured to determine elemental abundances; widths and shapes of lines can be measuredto determine velocity dispersion; equivalent widths can be measuredto determine surface brightnesses; etc. In general, any property that affects how electromagnetic radiation is absorbed or emitted by an astronomical object can potentially be studied through spectroscopy