13 billion years ago, our universe was dark. There were no stars or galaxies; only hydrogen gas remained after the Big Bang. Eventually, hydrogen atoms began to clump together to form stars, the first to exist, initiating an important phase in the evolution of the universe, known as the Epoch of Reionization.
“Defining the evolution of the Epoch of Reionization is extremely important for our understanding of astrophysics and cosmology”, clarifies Nichole Barry, about the signal that has been traveling through the universe for 12,000 million years, bringing us closer to understanding life. and death of the first stars. However, until now no one has been able to observe it. Fortunately, the results of the study and collecting Arxiv Astrophysical Journal, we come a little closer to that goal.
In the image of the Epoch of reionization provided by the experts and that we can see below, the neutral hydrogen, in red, is gradually ionized by the first stars, which are shown in white. The image was made by the Dark Ages Reionization and Galaxy Observation program at the University of Melbourne from the numerical simulations program (DRAGONS).
Since that time, 12 billion years ago, all the energy radiated by those stars filled the universe with a kind of fog, a sea of photons known as extragalactic backlight.
Astrophysicists believe that our universe, which is about 13.7 billion years old , began forming the first stars when it was a few hundred million years old. Since then, the universe has become a star-making factory.
Light of the observable universe
Astronomers estimate that the observable universe, a bubble 14 billion light-years in radius, representing how far we’ve been able to see since its inception, contains at least two trillion galaxies and one trillion trillion stars, but most are too far away and too faint to be seen with any current telescope.
The Epoch of Reionization is the 1 billion year period after hydrogen gas collapsed into the first stars, perhaps 100 million years after the Big Bang, through the ignition of stars and galaxies throughout the universe. These first bright objects flooded the universe with ultraviolet light that split or ionized all the hydrogen atoms between galaxies into protons and electrons to create the universe we see today.
A sign never seen before
In the present study, a team led by Nichole Barry exposes a 10-fold improvement in data collected by the Murchison Widefield Array (MWA), a collection of 4,096 dipole antennas installed in the remote interior of Western Australia.
The MWA, which began operation in 2013, was built specifically to detect electromagnetic radiation emitted by neutral hydrogen, a gas that comprised most of the infant universe in the period when the primordial soup of disconnected protons and neutrons generated by the Big Bang began to cool.
The neutral hydrogen that dominated space and time before and in the early Reionization Epoch radiated at a wavelength of approximately 21 centimeters. Stretched now over two meters due to the expansion of the universe, the signal persists, and detecting it remains the best theoretical way to explore conditions in the early days of the cosmos.
Hidden sign
However, doing so is incredibly difficult. “The signal we are looking for is over 12 billion years old,” explains Cathryn Trott of the International Center for Radio Astronomy Research at Curtin University in Western Australia. “It is exceptionally faint and there are many other galaxies between it and us. They get in the way and make it very difficult to extract the information we are looking for. “
Using 21 hours of raw data, the scientists explored new techniques to refine the analysis and exclude consistent sources of signal contamination, including ultra-weak interference generated by radio transmissions on Earth.
The result was a level of precision that significantly reduced the range in which the Epoch of Reionization could have started, introducing restrictions by almost an order of magnitude. “We can’t really say that this document brings us any closer to accurately dating the beginning or end of the Epoch of Reionization, but it does rule out some of the more extreme models,” the authors clarify. “What happened very quickly is now ruled out. That the conditions were very cold, too ”.
The results represent not only a step forward in the global quest to explore the early universe, but also establish an ideal framework for future research.
“We have around 3,000 hours of MWA data,” they explain, “and for our purposes some of it is more useful than others. This approach will allow us to identify which parts are the most promising and analyze them better than ever before.”
Referencia: N. Barry, M. Wilensky, C. M. Trott, B. Pindor, A. P. Beardsley, B. J. Hazelton, I. S. Sullivan, M. F. Morales, J. C. Pober, J. Line, B. Greig, R. Byrne, A. Lanman, W. Li, C. H. Jordan, R. C. Joseph, B. McKinley, M. Rahimi, S. Yoshiura, J. D. Bowman, B. M. Gaensler, J. N. Hewitt, D. C. Jacobs, D. A. Mitchell, N. Udaya Shankar, S. K. Sethi, R. Subrahmanyan, S. J. Tingay, R. L. Webster, J. S. B. Wyithe. Improving the EoR Power Spectrum Results from MWA Season 1 Observations. Astrophysical Journal, 2019 https://arxiv.org/abs/1909.00561
