The first few hundred million years after the Big Bang still holds many mysteries that we do not understand. One particular observation is out lack of sighting the first stars. There are some speculations as what they might be like but till now, they haven’t been seen directly as they lived way too far in the past and perished much too quickly. Our present technology and instruments are not good enough to spot them. In the meantime, though, we are working out better ways to spot them indirectly.
The Murchinson Widefield Array radio observatory in Australia has perceived a 10-fold improvement on the data from the early universe. Their new findings are reported in a paper currently available on the preprint server ArXiv and slated for publishing in The Astrophysical Journal.
The Australian observatory was designed with the sole objective of studying the Epoch of Reionization (EoR) i.e. the period when the formation of first stars happened and is named after what happened to hydrogen in this stage. Around 380,000 years after the Big Bang, the universe had finally cooled enough for the protons and electrons to form hydrogen atoms. Over hundreds of millions of years during the so-called cosmic dark ages, hydrogen collected in clouds until it ultimately collapsed into the first stars. The light of the first stars was so powerful that it stripped the electrons from the hydrogen in a process called ionization for the second time in the history of the universe.
Lead author Dr. Nichole Barry, from the University of Melbourne, said in a statement, “Defining the evolution of the EoR is extremely important for our understanding of astrophysics and cosmology. So far, though, no one has been able to observe it. These results take us a lot closer to that goal.”
The research team is focusing on a specific emission of neutral hydrogen known as the 21-centimeter line whose signal is difficult to capture as it is very weak and there are a massive number of other galaxies and objects between its sources and us.
The team gathered 21 hours of raw data from the observatory and applied different techniques to refine the analysis. Part of the emphasis was to ensure that potential sources of contamination like signals from Earth were detected and excluded with high accuracy. Their result significantly advances what we know about this mysterious epoch.
Co-author Professor Cathryn Trott, from the International Centre for Radio Astronomy Research at Curtin University in Western Australia, added, “We can’t really say that this paper gets us closer to precisely dating the start or finish of the EoR, but it does rule out some of the more extreme models. That it happened very rapidly is now ruled out. That the conditions were very cold is now also ruled out.”
Future observatories will no doubt, be able to study the first generation of stars better and provide answers to many mysteries left to solve.