User: When did the first supernovae occur?
Assistant: The first supernovae occurred about a billion years after the Big Bang. This is a very important and exciting time in our universe, because it is during this period that the first stars formed. The first stars were extremely massive and hot, and they radiated energy at such a high rate that they collapsed into black holes. These black holes then swallowed up the surrounding gas, and the gas was compressed to form the first stars.