Can someone help with this I don’t get it???

For this specific star, it would be magnesium

Explanation:

when you look at the spectrum of light for, in this case, a star, you are seeing a specific light signature, like a fingerprint. you have to compare the black lines of the star's light spectrum to the light spectrum of different gasses to see which ones match up. in this case, the lines in star 8's spectrum match the lines in the spectrum of magnesium.

the  frequency of a wave represents  the number of wavelengths that pass a specific point per second. the unit for  frequency  is hertz (hz).

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