4: Stellar Spectra
- Page ID
- 115277
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How do you collect a sample of a star? An astronomer can't scoop up a piece of a star and take it to a lab to learn its composition. They also can't measure the rotation or motion of a star using the same procedures that we measure the motion of a car or airplane due to their extreme distance. Instead, astronomers rely on different measurements by analyzing the light of the star. By analyzing the color of a star, astronomers can calculate its temperature. The next step in light analysis is to break the light into smaller pieces by wavelength, producing a spectrum. The analysis of spectra and the information derived from them is the focus of this chapter.
By the end of this section, you will be able to:
- Describe the structure of atoms and the components of nuclei
- Define the atomic mass unit
- Explain how emission line spectra and absorption line spectra are formed
- Explain how spectral lines and ionization levels in a gas can help us determine its temperature
- Explain how astronomers learn the composition of a gas by examining its spectral lines
- Describe how astronomers use spectral classes to characterize stars
- List the stellar properties that astronomers can learn about a star by studying its spectrum
- Describe the proper motion of a star and how it relates to a star’s space velocity
Thumbnail: The spectrum of the Sun, discussed in detail in Spectral Lines. (CC BY 4.0; N.A. Sharp/KPNO/NOIRLab/NSO/NSF/AURA via Wikimedia Commons).