How many generations of stars does the milky way contain?
Our sun is a Population I star. Population I or metal-rich stars are those young stars whose metallicity is highest. These are common in the spiral arms of the Milky Way galaxy. Population II are a previous generation of stars with relatively little metals. These objects formed during an earlier time of the universe and are common in the bulge near the centre of the galaxy and the galactic halo. Globular clusters also contain high numbers of Population II stars. Population III or metal-free stars are a hypothetical population of extremely massive and hot stars with virtually no metal content which are believed to have been formed in the early universe. They have not yet been observed directly, but indirect evidence for their existence has been found in a gravitationally-lensed galaxy in the very distant (therefore ancient) universe. There are no Population III stars known to exist in the Milky Way. So the answer is 2.
