What is Spectroscopy

Astronomical spectroscopy is one branch of spectroscopy that deals with the physical and chemical properties of astronomical objects. It is a technique that measures the absorbed, emitted or scattered light of materials. Spectroscopy´s role in astronomy involves the determination of a variety of stellar object´s properties, such as temperature, distance and age, among others. Spectroscopy is used to study the electromagnetic radiation (visible light, radio, infrared, ultra-violet, x-ray and gamma rays) of stars and other far away space objects.

The universe is so vast and the distances extremely immense that the only way to know where they are is by the observing the light they emit. This has allowed astronomers to determine most of their properties. The use of electromagnetic radiation as a means to study the properties of heavenly objects has allowed astronomers to determine everything we know about those far away objects. The outer portion of stars contains extremely hot gases. These gases radiate energy at some portion of the electromagnetic spectrum. Astronomers use special instruments, such as spectroscopes, to read the spectral produced by light received from distant objects.

The study of astronomical objects using spectroscopy began by the observations made by Isaac newton of the sun´s light. Later, spectroscopy was used to classify stars based on their type of spectra. Over time, spectral lines were discovered to be related to the temperature of a star. It was also discovered that the chemical composition of a star could be determined from the examination of the absorption lines, thus, determining the elements present in a star. In 1868, a scientist named Norman Lock detected the element Helium in the Sun by observing the spectral lines in the Sun´s spectrum.

Today, spectroscopy is used to study a number of properties in stars, including composition, age, distance, luminosity, mass, velocity, etc. Astronomers use a spectroscope, which is an instrument that splits passing light into its component colors, allowing astronomers to obtain the chemical and physical characteristics of stellar objects. In the 1920s, Edwin Hubble discovered that the universe is expanding by looking at the spectra of galaxies. In the 1950s, the light spectrum of objects known as quasar was detected. The absorption lines that were found in the red color of the spectrum suggested that theobjects were extremely distant, and as a consequence, very luminous.

Astronomers study the composition of asteroids and planets by analyzing the light they reflect from their parent star. The reflected light contains absorption lines of the minerals contained in the rocks of the stellar body. In this way it was discovered that most asteroids are made of metals and silicates. The absorption spectral lines of planets are produced when molecules absorb light at given wavelengths and reemit them in all directions. The study of comets involves analyzing the emission lines produced by gases and molecules excited by sunlight.

Celestial objects, which abound in the sky, are full of information needing to be interpreted. The study of these objects, ranging from stars, asteroids, quasars, black holes, galaxies, etc., can tell us about their distance, size and the speed at which they´re moving from us. According to arizona.edu, spectroscopy studies the component colors contained within an object spectrum. By practicing the analysis of an object light spectrum, astronomers are able to deduce the physical properties of objects, including neutron stars, black holes, galaxies, planets, among many other stellar objects.