Final answer:
Spectroscopy is the study of light from celestial objects to determine their composition, which provides vital information for understanding the nature of stars and galaxies.
Step-by-step explanation:
Spectroscopy is a technique used to determine the composition, temperature, motion, and various characteristics of distant celestial objects by studying their emitted light. When light from an object such as a star or galaxy passes through a spectrometer, it is split into a spectrum of colors, each corresponding to different wavelengths. The patterns of absorption and emission lines within this spectrum provide astronomers with clear information about the chemical makeup of these objects.
Astronomers use spectroscopy to 'sample' the stars since they are too far away for us to physically collect samples from. By analyzing the spectra, which carry unique fingerprints for different elements, scientists can infer what stars and galaxies are made of, thus enabling them to develop theories about how these objects shine and evolve over time.
The correct answer to the student's question is A: the use of light from a distant object to determine what the object is made of.