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searching for the first stars in the universe



  And then there was light: the search for the first stars in the universe
In this image of the era of re-energization, neutral hydrogen, in red, was gradually ionized by the first stars shown in white. Image courtesy of the University of Melbourne's Reionization and Galactic Observation Program by Numerical Simulations (DRAGONS). Credit: Paul Gayle and Simon Much

Astronomers are closing in on a signal that has been circling the universe for 1

2 billion years, bringing them closer to understanding the lives and deaths of the earliest stars.


In an article on the pre-press site arXiv and will soon be published in the Astrophysical Journal by a team led by Dr Nicole Ni Bari of the University of Australia at Melbourne and the ARC Center for Excellence in Celestial Astrophysics 3 Dimensions (ASTRO 3-D) reports a 10-fold improvement in data collected by Murchison Widefield Array (MWA), a collection of 4096 dipole antennas placed in the far west of Western Australia.

MWA, which started operating in 2013, was created specifically to detect electromagnetic radiation emitted by neutral hydrogen, a gas that makes up the majority of the infant universe at a time when the soup of protons and neutrons is generated. from the Big Bang, it started to cool.

Eventually, these hydrogen atoms began to cluster together to form stars – the first to exist – initiating a major phase in the evolution of the universe, known as the Era of Reonization, or EoR.

"Defining Evolution The concept of EoR is extremely important to our understanding of astrophysics and cosmology," explains Dr. Barry.

"So far, however, no one has been able to observe it. These results take us much closer to that end."

In this simulation of the reonization era, neutral hydrogen in red is gradually ionized by the first stars shown in white. The video was made by the University of Melbourne's Galaxy Reionization and Observation Program of Dark Ages and Digital Simulations (DRAGONS). Credit: Paul Gayle and Simon Much

Neutral hydrogen, which dominates in space and time before and during the early EoR period, emitted a wavelength of approximately 21. Extended now to just over two meters due to the expansion of the universe, the signal continues – and discovery it remains theoretically the best way to study the conditions in the early days of space.

However, this is incredibly difficult.

"The signal we are looking for is more than 12 billion years old," explains ASTRO 3-D member and co-author Associate Professor Catherine Trot of the International Center for Radio Astronomy Research at Curtin University in Western Australia.

"It's extremely weak and there are many other galaxies between it and us. They are difficult and make it very difficult to retrieve the information we are looking for. "

In other words, the signals recorded by MWA – and other EoR hunting devices, such as the Hydrogen Era of the Rehasation Array in South Africa and the Low Frequency Array in the Netherlands, are extremely mixed.

Using 21 hours of raw data e- Dr. Barry, co-authored with author Mike Wilensky of the University of Washington, USA, and his colleagues explored new techniques for refining, analyzing and excluding sequential sources of signal pollution, including ultra-weak interference generated by radio transmissions on Earth.

  And then there was with etlina: the search for the first stars in the universe
Dr. Nicole Ne Barry The Murchison Widefield Array (MWA) Credit: Ruby Byrne

The result was a level of precision that significantly reduced the range in which an EoR could have started, pulling limits by almost an order.

"In fact, we can't say that this document brings us closer to accurately dating the beginning or end of an EoR, but it does rule out some of the more extreme patterns," says Professor Trot.

"That a lot has happened fast, now it's off. That the conditions were very cold, now also excluded. "

Dr. Barry said that the results not only are a step forward in the global quest for a study of the infant universe, but also create a framework for further research.

" We have about 3000 hours of MWA data. " "she explains," and for our purposes, some are more useful than others. This approach will allow us to identify which bits are most promising and analyze them better than we could ever do. "


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More information:
MWA EoR Power Spectrum Improvement Season 1 Observations, arXiv: 1909.00561 [astro-ph.IM] arxiv.org/abs/1909.00561

Provided by
ARC Center of Excellence for All Celestial Astrophysics in 3D

Reference :
And then there was light: looking for the first stars in the universe (2019, September 9)
retrieved 9 September 2019
from https://phys.org/news/2019-09-stars-universe.html

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