The vast expanse of the universe is home to countless celestial bodies that never fail to fascinate us. From the twinkling stars above to distant galaxies and colorful nebulae, the cosmos has inspired our curiosity and imagination. Spectroscopy has emerged as a game-changing method in revolutionizing our understanding of the universe, thanks to the rapid development of astronomical tools and techniques. “In this post, we will give you a short tour of the application of spectroscopy in astronomy.

Let’s dive in!

What is the principle of spectroscopy?

Spectroscopy is a fascinating technique that studies the light emitted or absorbed by matter. It’s like breaking down a rainbow into its colors but on a much more sophisticated scale. When light interacts with an object such as a star, planet, or nebula, it provides valuable information encoded in its spectrum. Scientists utilize this information to analyze the object’s composition, temperature, motion, and other characteristics.

Spectroscopy is a scientific technique that separates light into its component wavelengths, similar to a prism dispersing sunlight into a range of colors. When this separated light passes through a medium or substance, specific wavelengths are either absorbed or emitted, resulting in distinct dark or bright lines in the spectrum. These lines serve as a unique fingerprint for each element or molecule present in the observed object. Through the analysis of these spectral lines, scientists can determine the elements composing the object and their relative abundances, offering valuable insights into its properties.

Related article: Electromagnetic Radiation in Astronomy: An Overview

How is spectroscopy used in astronomy?

Astronomers used spectroscopy as a tool to study the universe. By studying the spectra of celestial objects, they can determine the chemical compositions, temperatures, densities, and even the object’s movement in space. Therefore, we can understand the evolution and nature of stars, galaxies, and other celestial phenomena by utilizing this abundance of information.

There are several spectroscopic methods at our disposal to study the intricacies of the cosmos. Each technique provides us with a unique perspective into the universe, allowing us to investigate different aspects of celestial bodies and phenomena.

The table below provides an overview of different spectroscopic techniques utilized in astronomy and some of the prominent telescopes or tools associated with each technique.

Spectroscopic Technique	Description	Telescopes/Tools
Emission Spectroscopy	Examines light emitted by celestial objects	Spectrographs mounted on telescopes, like Keck Observatory
Absorption Spectroscopy	Analyzes light passing through a medium, revealing absorption lines	Hubble Space Telescope, VLT (Very Large Telescope)
Stellar Spectroscopy	Studies spectra of stars to determine properties	The James Webb Space Telescope, Gemini Observatory
X-ray Spectroscopy	Observes high-energy phenomena	Chandra X-ray Observatory, XMM-Newton
Ultraviolet Spectroscopy	Studies energetic regions in the universe	Hubble Space Telescope, Swift Observatory
Infrared Spectroscopy	Detects infrared emissions from celestial objects	Spitzer Space Telescope, Atacama Large Millimeter/submillimeter Array (ALMA)

Recent discoveries via spectroscopy in astronomy research

Spectroscopy has played a crucial role in the study of exoplanet atmospheres. Through space-based telescopes and ground-based observatories, scientists have been able to identify various molecules, such as water, methane, and carbon dioxide, in the atmospheres of distant exoplanets, providing valuable information about their potential habitability and composition.

Recently, a study reported that the atmosphere of WASP-121 b is dynamic and could form cyclones and other weather activities. In addition, the variability in the chemical composition of the exoplanet’s atmosphere including the presence of water vapor, absorbers of visible radiation (VO and TiO), hydrogen ions (H− ), and atomic species (Ba, Ca, Cr, Fe, H, K, Li, Mg, Na, V, and Sr) also has been detected. The properties of the WASP-121 atmosphere were robustly characterized via the combined phase-curve atmospheric retrieval technique [Changeat et al., 2024].

Another study of WASP-121b found that the eastern region of the dayside hemisphere is generally hotter than the western region. This analysis was based on phase-curve measurements using the JWST NIRSpec (Near Infrared Spectrograph) instrument. Additionally, it suggests the possible presence of silicate clouds in the nightside hemisphere.[Mikal-Evans et al., 2022].

Fun Fact:

WASP-121 b  a.k.a Ultra-hot Jupiter condition is bizarre. Its size is a bit larger than Jupiter’s. In addition, it is very close to its parent star and completes one cycle of orbit in just 1.27 days! This exoplanet is also tidally locked – the same hemisphere always faces the star. However, it is inhabitable and extremely hot (3,450 degrees Fahrenheit on the star-facing side of the planet) [https://phys.org/news/2024-01-nasa-hubble-exoplanet-atmosphere-years.html].

Summary

Spectroscopy is fundamental in astronomical research, allowing scientists to analyze the features and data of celestial objects. As we enhance our spectroscopic methods and tools, we will reveal more mysteries of the universe. Many discoveries and updates on astronomy await us in the future.

Reference

Changeat, Q., Skinner, J. W., Cho, J. Y., Nättilä, J., Waldmann, I. P., F., A., Dyrek, A., Edwards, B., Joshua, M., Morello, G., Skaf, N., Tsiaras, A., Venot, O., & Yip, K. H. (2024). Is the atmosphere of the ultra-hot Jupiter WASP-121b variable? ArXiv. /abs/2401.01465

Mikal-Evans, N., Kataria, T., Bourrier, V., et al. “The First Phase-Curve Measurement of the Ultrahot Jupiter WASP-121b with JWST NIRSpec”. (2022). The Astrophysical Journal Letters. 943 (2). DOI: 10.3847/2041-8213/acb049

https://phys.org/news/2024-01-nasa-hubble-exoplanet-atmosphere-years.html