Archaeology is like a big jigsaw puzzle with no picture to follow as a guide. Archaeologists try to piece together many relics from the past to understand how a culture was born and how its people lived. Today, astronomers are trying to become archaeologists as well — galactic archaeologists. They’re piecing together the history of our Milky Way galaxy by looking for groups of related stars — the possible remnants of big star clusters, or the smaller galaxies that the Milky Way has taken over. The key to deciphering the galaxy’s history is the chemistry of its stars. Most stars are born in large clusters, which form from giant clouds of gas and dust. The stars in each cluster share the same chemical makeup. Over time, the clusters break apart and the stars disperse. But the stars retain the chemical “memory” of their birthplace. One new survey is reading the chemical “barcodes” of millions of individual stars. Slight variations in the amounts of different elements should show which sta
