An international team of scientists has found a clue as to what happened in the universe after the Big Bang. They claim that just after the big bang, a dense hydrogen fog that was seen across the universe was completely burned off in some isolated, low-density regions of the universe. A few hundred million years later, reionisation took place in the dense, crowded regions of the universe.
Previously, astronomers claimed that just after big bang, a dense hydrogen "fog" settled over the universe. During this time, a lot of the light produced by the first stars could only travel short distances before it was absorbed by the fog. They call this period the "dark ages" of the universe, but little is known about what was happening at this time.
Now scientists have found that hydrogen fog was burned off first in isolated, low-density regions of the universe. They also found that galaxies in crowded regions of the universe were more likely to be shrouded in very dense pockets of hydrogen fog. Such dense regions would therefore require larger numbers of light sources and more time to burn off the fog compared to regions with relatively light fog.
Scientists discovered this when they studied several reionisations that took place around three galaxies, including the Milky Way. "We used nearby galaxies to understand something that happened long ago, in much the same way fossils are used to understand earth's history," said Duncan Forbes, professor at the Swinburne University of Technology.
"We can see regions around galaxies where reionisation has just finished and use that information to understand important questions about the dark ages: What were the first stars like; how were the first galaxies formed; and were there many supermassive black holes," he added.
"Understanding how reionisation moved through the universe is very challenging but of enormous importance in astronomy. Our technique provides a novel way to tackle this problem," said Dr Lee Spitler, astrophysicist at the Swinburne University of Technology, in a statement.
Scientists claim that further studies will help them understand more about the dark ages and the evolution of the universe.