In this blog post, we will look at how spectroscopic analysis was born and why it became a turning point that changed the course of scientific history, from material analysis to astronomical research.
In the mid-19th century, chemist Robert Bunsen was conducting research on the unique flame colors of substances that appear in flame reactions. He devised an improved burner that removed the color of the burner flame, making it easier to distinguish the flame colors of different substances. His improved burner provided a more stable and cleaner flame than previous burners, greatly contributing to the accuracy of experimental results. However, it was difficult to distinguish between substances containing two or more metals because their flame colors overlapped. Physicist Gustav Kirchhoff proposed analyzing the flames using a prism, and the two collaborated to develop a spectroscopic analysis method that separated the colors of the flames. This spectroscopic analysis method separated the complex colors of the flames, enabling the unique spectra of each component to be clearly identified. This led to an achievement that will remain in the history of science.
They conducted experiments by passing the light emitted from flame reactions through a prism to disperse it into bands, and then observing it through a telescope. Light disperses into bands because the shorter the wavelength, the greater the angle of refraction. Using this method, they systematically investigated the spectra of alkali metals and alkali earth metals and discovered the compounds that contain them. In the process, they concluded that the positions of bright lines scattered in the spectrum of a specific metal are always the same regardless of the temperature of the flame, whether the metal exists as a single element or in combination with other elements. This was an innovative method that enabled the accurate identification of the constituent elements of compounds without the use of existing chemical analysis methods. This led to the birth of spectroscopic analysis, a method of accurately identifying the elements of compounds without relying on traditional analytical chemistry methods that use chemical reactions. The effectiveness of this method was proven by their discovery of two new metallic elements, cesium and rubidium.
In 1859, Kirchhoff extended this method to the field of astronomy. By comparing two adjacent bright lines in the sodium spectrum observed in flame reaction experiments with the black lines discovered in the solar spectrum by Joseph von Fraunhofer in the 1810s using a prism, he was able to explain the cause of the black lines in the solar spectrum. He confirmed that Fraunhofer’s D line overlapped with the bright lines unique to sodium at the same wavelength among the black lines in the spectrum of sunlight, and interpreted that the D line was caused by sodium present in the relatively cold part of the sun, the solar atmosphere. This is because the sodium in the solar atmosphere absorbs the light corresponding to the D line wavelength from the light emitted from the hotter parts of the sun. When looking at the spectrum of sunlight, black lines appear at the wavelengths of light absorbed by certain elements in the cold solar atmosphere, in addition to the D line. These black lines appear in the same positions as the bright lines in the spectrum produced by those elements in a flame reaction.
Subsequently, through the application of this principle, it was discovered that other elements such as iron and helium also exist in the solar atmosphere, and the same principle was applied to the study of other stars. Fellow scientists evaluated this discovery, saying that spectroscopic analysis, which can be applied to physics, chemistry, and astronomy, revealed the chemical composition of the atmosphere of celestial bodies, thereby revealing the unity of the universe and contributing to the recognition of the principles of nature that exist everywhere in the universe. This technology accelerated the development of astrophysics and played a major role in deepening our understanding of the universe. For example, spectroscopic analysis is an important tool for determining the chemical composition of atmospheres when exploring the possibility of life on planets other than Earth.
The introduction of spectroscopic analysis ushered in a new era of scientific research. Scientists are now able to analyze chemical compositions not only in laboratories but also in distant celestial bodies, which has revolutionized astronomical research. This has given us important clues for understanding the composition of planets and stars outside our solar system and for exploring the origins of the universe. These discoveries are still valid today and continue to contribute greatly to the advancement of modern science. The collaboration between Bunsen and Kirchhoff is a perfect example of the nature of scientific discovery, and their research continues to inspire subsequent researchers.
Scientific discoveries are often made in unexpected ways and are made possible through collaboration between different fields. The research of Bunsen and Kirchhoff went beyond simply creating a new analytical method; it is a prime example of the importance of collaboration and convergence between scientists. Their achievements continue to shine today and serve as an important foundation for future scientific exploration.
Bunsen and Kirchhoff’s research was the result of academic curiosity and perseverance, and was achieved through the creativity and spirit of cooperation between the two scientists. This research did not stop at success in the laboratory, but presented various applications and caused a great stir in the scientific community. Their cooperation showed that science is not the study of individual fields, but shines even brighter when different disciplines come together to create synergy. As a result, subsequent researchers were able to continue their research in greater depth, utilizing their own expertise, and contributing to the advancement of science.
