“Far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy lies a small unregarded yellow sun. Orbiting this at a distance of roughly ninety-two million miles is an utterly insignificant little blue green planet whose ape-descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea.” -Douglas Adams
If you want to know how many and what type of chemical elements are present in a star system, you need to make a dizzying, intricate array of observations. You need to break up the light from the star into its component wavelengths and look for the signatures of absorption and emission lines corresponding to each individual element you’re seeking, while simultaneously accounting for effects like temperature and ionization.
This is made extra difficult by the fact that most of the Milky Way is obscured by gas, dust and other neutral matter. But thanks to the infrared instruments on the wide-field Sloan Digital Sky Survey, over 150,000 stars have had their spectra taken, located throughout the Milky Way, and the results are spectacular. In particular, the center of our galaxy has more heavy elements than we do, potentially meaning that it could have begun harboring life billions of years earlier.