Our Milky Way galaxy contains hundreds of billions of stars, each one radiating light and also creating chemical elements inside it through nuclear fusion reactions: hydrogen becoming helium, helium becoming carbon and oxygen, and so on. The cartoon below shows the structure of our galaxy in terms of the ages and locations of stars in it. Accompanying that information are the spectra of each kind of star. I will mention that the patterns of dark lines in their spectra indicate that all these stars have the same surface temperature.
Our Milky Way galaxy contains hundreds of billions of stars, each one radiating light and also creating chemical elements inside it through nuclear fusion reactions: hydrogen becoming helium; helium becoming carbon and oxygen, and so on. The cartoon below shows the structure of our galaxy in terms of the ages and locations of stars in it. Accompanying that information are the spectra of each kind of star. I will mention that the patterns of dark lines in their spectra indicate that all these stars have the same surface temperature.
Ca Fe
Halo star Age 12 billion years Old Disk star Age 4.5 billion years Young Disk star Age 0.5 billion years
The element producing each dark line is listed above it for each spectrum. Those labeled "H" are all hydrogen lines; the others are calcium (Ca), iron (Fe), and sodium (Na).
Time to be a detective! What other property of stars in our galaxy is a function of their age? Explain how you came to that conclusion.