Distance Learning Module: Intro to Spectroscopy
Spectroscopy is the study of how matter (all the “stuff” that makes up the universe) interacts with electromagnetic radiation (a form of energy). Before we move on with this idea, let’s back up and cover some important background words and ideas:
Electromagnetic radiation is energy that moves outward (radiates) away from its source in a series of waves.
The electromagnetic spectrum is a way of arranging all the types of electromagnetic radiation, according to their wavelength. Types of radiation with short wavelengths (a small distance from the top of one wave to the top of the next wave) are on one end of the spectrum. Types of radiation with long wavelengths (a lot of distance between the tops of the waves) are on the other end.
Types of energy along the electromagnetic spectrum include gamma rays, X-rays, ultraviolet light, visible light, infrared, microwaves, and radio waves—as we can see in this illustration from NASA:
Optics is a branch of physics that involves the study of the middle segments of the electromagnetic spectrum: visible light, ultraviolet, and infrared.
Now back to spectroscopy…
a prism is a 3-dimensional shape that splits white light into the many frequencies that make it up (image credit: wikimedia commons)
Traditionally, spectroscopy involved the use of prisms to study the properties of visible light. Today, scientists use sophisticated instruments to study all portions of the electromagnetic spectrum—including X-ray, gamma, and UV rays. Spectroscopy may overlap with optics, or it may involve parts of the spectrum that fall outside the focus of optics. Spectroscopy involves all sorts of interactions between light and matter—for example absorption and refraction.
Practical Applications
Spectroscopy has many applications in physics, astronomy, chemistry, medicine, and various other branches of science. For example, it is often used to identify the nature of compounds in an unknown sample. Spectroscopic tools and data are also used to monitor the progress of chemical processes; to assess the purity of products; to measure the effect of electromagnetic radiation on a sample; and to determine the intensity or duration of exposure to a radiation source.
Laboratory of electron spectroscopy at Gdańsk University of Technology in Poland, 2017 (image credit: wikimedia commons/ Dominik Bejma and Marta Kowalkińska)
Spectroscopy can be classified in several ways—according to:
the type of energy (electromagnetic radiation) being studied—e.g. infrared, gamma, or X-ray
the type of interaction being studied—e.g. emission, absorption, or scattering
the type of material being studied—e.g., atoms, crystals, molecules, atomic nuclei
the measurement process or tools used—e.g. satellite or antenna
Astronomical Spectroscopy
Spectroscopy allows scientists to study the properties of celestial objects—such as stars, planets, nebulae, galaxies—and of interstellar space. Using special equipment like a spectroscope, astronomers can split light from space into a spectrum and examine its spectral lines to infer what compounds are emitted or absorbed.
The first direct detection and chemical analysis of the atmosphere of an exoplanet, in 2001. Sodium in the atmosphere filters the starlight of HD 209458 as the giant planet passes in front of the star (image credit: NASA)
illustration of james webb telescope in action (image credit: spacetelescope.org/Northrup Grumman)
The Hubble Space Telescope can view objects in ultraviolet, visible and infrared light. The James Webb Space Telescope, set to launch in 2021, is equipped with instruments that will help to build on the knowledge that came from Hubble. Watch this video from NASA about how space telescopes break light into different wavelengths:
Spectroscopy is to thank for countless discoveries about the nature of our universe! It is responsible for:
Recording a black hole’s signature, uncovering gas swirling at hundreds of miles per second around a black hole at the center of another galaxy
Providing first direct detection of the atmosphere of a planet orbiting a star outside our solar system
Detecting an organic molecule in the atmosphere of a planet orbiting another star
Finding what were thought to be randomly distributed, nearby primordial clouds of hydrogen may actually be associated with galaxies or clusters of galaxies
Showing that massive clouds of ionized gas are raining down from our galaxy’s halo and intergalactic space, and will continue to provide fuel for the Milky Way to keep forming stars
Fingerprinting the distant universe using the light from a quasar, allowing astronomers to probe the raw materials from which galaxies form and determine how this gas was assembled into the complex structures of the present-day universe
(above list courtesy of hubblesite.org)
Spectroscopy is even responsible for helping scientists discover and analyze a number of exoplanets.
Above: A beam of light coming to Earth from a distant quasar passes through numerous intervening gas clouds in galaxies and in intergalactic space. These clouds of primeval hydrogen subtract specific colors from the beam. The resulting absorption spectrum, recorded by Hubble Space Telescope’s Imaging Spectrograph (STIS) is used to determine the distances and chemical composition of the invisible clouds. (Image credit: NASA/ESA)
Below: This highly detailed image of the Crab Nebula combines data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum. The picture includes data from five different telescopes: the Spitzer Space Telescope (infrared) in yellow; the Karl G. Jansky Very Large Array (radio) in red; Hubble Space Telescope (visible) in green; XMM-Newton (ultraviolet) in blue; and Chandra X-ray Observatory (X-ray) in purple. (Image credit: NASA)
