When the first black holes were born?

“Most of the galaxies in the universe, including our own Milky Way harbors massive black holes that vary in mass from one million to 10 billion times the size of our sun. To find them, astronomers look for the enormous amounts of radiation emitted during the period in which these black holes are “active,” ie, incorporated matter. It is believed that these gas clouds are responsible for making black holes grow. Now a team of astronomers from the University of Tel Aviv, including Hagai Hetz teacher and his student Benny Trakhtenbrot, determined that was what happened in the first major growth of the largest black holes occurred when the universe was only 1.2 billion years – and not between 2 billion and 4 billion years ago, as it was believed earlier – and they are growing very fast. The study results were published in the Astrophysical Journal. The new research is based on observations made by some of the largest telescopes in the world, as the “Gemini North”, located atop Mauna Kea in Hawaii, and the “Very Large Array” on Cerro Paranal in Chile. The data obtained from these advanced instruments showed that the black holes that were active when the universe was 1.2 billion years old are ten times smaller than the large black holes seen some time later. However, they are growing very fast. The team found that the first black holes, those that started the growth process when the universe was only a few hundred million years, had masses between 100 and 1,000 times the mass of the sun. These black holes may be related to the first stars in the universe. This study is part of a seven-year project developed by the University of Tel Aviv and designed to follow the evolution of the largest black holes and compare their evolution with the evolution of the galaxies in which they reside.”