Astronomers have discovered the oldest known source of oxygen in the universe. This oxygen was found in a distant galaxy, located 12 billion light-years away from Earth. The oxygen was produced by the first stars that formed in the early universe, and is estimated to be about 13.2 billion years old. This discovery provides new insight into the evolution of the universe and how it has changed over time. It also helps to explain why the universe is filled with oxygen today.