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10 марта 2018, 05:16

Astronomers Detect Evidence of Earliest Stars in the Universe

Stay on target

Astronomers discovered evidence of the first light of some of the first stars.

Using a radio antenna, they detected faint signals of hydrogen gas, possible only in the presence of the earliest stars—which likely began blinking on some 180 million years after the Big Bang.

“This is the first real signal that stars are starting to form, and starting to affect the medium around them,” study co-author Alan Rogers, a scientist at MIT’s Haystack Observatory, said in a statement.

“What’s happening in this period is that some of the radiation from the very first stars is starting to allow hydrogen to be seen,” he continued. “It’s causing hydrogen to start absorbing the background radiation, so you start seeing it in silhouette, at particular radio frequencies.”

Scientists detected the primordial hydrogen gas using EDGES (Experiment to Detect Global EoR Signature), a ground-based radio antenna installed in Western Australia.

The instrument, about the size of a small table, detects radio waves from the entire sky. Designed and constructed by Rogers and the Haystack Observatory team, it boasts some additions by study co-authors Judd Bowman of Arizona State University, and Thomas Mozdzen, Nivedita Mahesh, and Raul Monsalve from the University of Colorado.

Many eons ago, the universe was a dark, empty place; its most abundant element, hydrogen, was virtually invisible. Then the first stars ignited to provide ultraviolet radiation, which researchers believe activated hydrogen atoms.

Rogers & Co. have been using EDGES to look for the earliest traces of hydrogen, to pinpoint when the first stars turned on.

“There is a great technical challenge to making this detection,” according to Peter Kurczynski, program director for Advanced Technologies and Instrumentation in the Division of Astronomical Sciences at the National Science Foundation.

“Sources of noise can be a thousand times brighter than the signal they are looking for,” he said. “It is like being in the middle of a hurricane and trying to hear the flap of a hummingbird’s wing.”

A view of the EDGES antenna, in Western Australia (via Judd Bowman/Arizona State University)

Built to detect radio waves from the entire sky, EDGES was originally tuned to a frequency range of 100 to 200 megahertz. However, when researchers switched the system to a lower 50-to-100-megahertz range, “we started seeing things that we felt might be a real signature,” Rogers said.

A dip in the radio waves (at around 78 megahertz) suggests the OG hydrogen gas was colder than previously thought.

The full study, supported by funding from the National Science Foundation, was published this week by the journal Nature .

“This is exciting because it is the first look into a particularly important period in the universe, when the first stars and galaxies were beginning to form,” Lonsdale said. “This is the first time anybody’s had any direct observational data from that epoch.”

Here’s to hoping it isn’t the last time.

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Source: https://www.geek.com/science/astronomers-detect-evidence-of-earliest-stars-in-the-universe-1732551/?source=science