In a new study, researchers describe observations of a distant galaxy, far enough away to be seen as it was a mere 700 million years after the Big Bang (As of this writing, it’s been about 13.8 billion years since the Big Bang). These observations turned up both the most distant oxygen ever observed and new clues about the cosmic phase shift known as reionization.

Early in the Universe’s history, there were no stars and little of any elements heavier than hydrogen and helium. When the first stars began to appear, they made two changes in the Universe around them. First, they began to create some of the heavier elements. Second, they started ionizing the hydrogen gas, stripping the electrons off it and leaving it electrically charged.

This second process is called reionization, since hydrogen started out ionized after the Big Bang, and only turned neutral after the Universe cooled. We don’t fully understand the reionization era of the Universe’s history, making it a major point of study.