Brown: Scientists Inch Closer Than Ever to Signal from Cosmic Dawn

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Brown: Scientists Inch Closer Than Ever to Signal from Cosmic Dawn

Post by bystander » Thu Nov 28, 2019 12:06 am

Scientists Inch Closer Than Ever to Signal from Cosmic Dawn
Brown University | 2019 Nov 26

Researchers using the Murchison Widefield Array radio telescope have taken a new and significant step toward detecting a signal from the period in cosmic history when the first stars lit up the universe.

Around 12 billion years ago, the universe emerged from a great cosmic dark age as the first stars and galaxies lit up. With a new analysis of data collected by the Murchison Widefield Array (MWA) radio telescope, scientists are now closer than ever to detecting the ultra-faint signature of this turning point in cosmic history.

In a paper on the preprint site arXiv and soon to be published in The Astrophysical Journal, researchers present the first analysis of data from a new configuration of the MWA designed specifically to look for the signal of neutral hydrogen, the gas that dominated the universe during the cosmic dark age. The analysis sets a new limit — the lowest limit yet — for the strength of the neutral hydrogen signal. ...

Despite its importance in cosmic history, little is known about the period when the first stars formed, which is known as the Epoch of Reionization (EoR). The first atoms that formed after the Big Bang were positively charged hydrogen ions — atoms whose electrons were stripped away by the energy of the infant universe. As the universe cooled and expanded, hydrogen atoms reunited with their electrons to form neutral hydrogen. And that’s just about all there was in the universe until about 12 billion years ago, when atoms started clumping together to form stars and galaxies. Light from those objects re-ionized the neutral hydrogen, causing it to largely disappear from interstellar space.

The goal of projects like the one happening at MWA is to locate the signal of neutral hydrogen from the dark ages and measure how it changed as the EoR unfolded. Doing so could reveal new and critical information about the first stars — the building blocks of the universe we see today. But catching any glimpse of that 12-billion-year-old signal is a difficult task that requires instruments with exquisite sensitivity. ...

First Season MWA Phase II EoR Power Spectrum Results at Redshift 7 ~ W. Li et al
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