How do astronomers determine which elements are present in distant stars or galaxies?

• A. By measuring the temperature of the star
• B. By calculating the mass of the star
• C. By observing the color of the star with the naked eye
• D. By analyzing the unique emission spectra produced by each element

Answer: (D)

Verified step by step guidance

1. Understand that each element emits or absorbs light at specific wavelengths, creating a unique pattern called an emission or absorption spectrum.
2. Astronomers collect light from distant stars or galaxies using telescopes equipped with spectrometers, which spread the light into its component wavelengths.
3. By examining the resulting spectrum, astronomers look for characteristic lines—bright lines for emission spectra or dark lines for absorption spectra—that correspond to specific elements.
4. Compare the observed spectral lines with known reference spectra of elements obtained in laboratories to identify which elements are present in the star or galaxy.
5. This method allows astronomers to determine the chemical composition of distant celestial objects without needing to physically sample them.