Question

how do spectrographs help astronomers classify stars?
○ they determine the size of stars.
○ they evaluate the color of stars.
○ they measure the brightness of stars.
○ they analyze the composition of stars.

Explanation:

Spectrographs split starlight into spectra, where dark/bright lines correspond to specific elements present in the star. By analyzing these spectral lines, astronomers can identify the star's chemical composition, which is a key factor in stellar classification. Other options: size is determined via interferometry or eclipsing binaries, color via photometry, brightness via photometers.

Answer:

They analyze the composition of stars.