EDGES instrument

An Absorption Profile Centered at 78 megahertz in the Sky-averaged Spectrum

Anonymous — Thu, 01 Mar 2018 15:32:43 +0000

An Absorption Profile Centered at 78 megahertz in the Sky-averaged Spectrum Anonymous (not verified) Thu, 03/01/2018 - 08:32

Judd D. Bowman Alan E. E. Rogers Raul A. Monsalve Thomas J. Mozdzen & Nivedita Mahesh

From Nature: After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. The profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions. This discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. Astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude. The low-frequency edge of the observed profile indicates that stars existed and had produced a background of Lyman-α photons by 180 million years after the Big Bang. The high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later. Read more...

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Did Dark Matter Make The Early Universe Chill Out?

Anonymous — Wed, 28 Feb 2018 15:58:22 +0000

Did Dark Matter Make The Early Universe Chill Out? Anonymous (not verified) Wed, 02/28/2018 - 08:58

Nell Greenfieldboyce

From NPR: Scientists have probed a period of the universe's early history that no one has been able to explore before — and they got a surprise: It was far colder in the young universe, before the first stars blinked on, than astronomers previously thought.

What's more, that cosmic chill may have come from previously unknown interactions between normal matter and mysterious, so-called dark matter, according to two new reports in the journal Nature.

If so, it's the first time scientists have observed any effect of dark matter other than its gravitational pull.

All of this comes from an experiment that detected a faint radio signal from primordial hydrogen gas in the young universe, just 180 million years after the Big Bang. Read more...

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When Stars Were Born: Earliest Starlight’s Effects Are Detected

Anonymous — Wed, 28 Feb 2018 15:54:24 +0000

When Stars Were Born: Earliest Starlight’s Effects Are Detected Anonymous (not verified) Wed, 02/28/2018 - 08:54

Dennis Overbye

From The New York Times: It was morning in the universe and much colder than anyone had expected when light from the first stars began to tickle and excite their dark surroundings nearly 14 billion years ago.

Astronomers using a small radio telescope in Australia reported on Wednesday that they had discerned effects of that first starlight on the universe when it was only 180 million years old. The observations take astronomers farther back into the mists of time than even the Hubble Space Telescope can see and raised new questions about how well astronomers really know the early days of the cosmos, and about the nature of the mysterious so-called dark matter whose gravity sculpts the luminous galaxies.

“We have seen indirectly evidence of very early stars in the universe — stars that would have formed by the time the universe was only 180 million years old,” said Judd Bowman of Arizona State, leader of the experiment known as EDGES, for Experiment to Detect Global EoR, in an email. Dr. Bowman and his colleagues published their results in Nature Wednesday. Read more...

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Astronomers detect light from the Universe’s first stars

Anonymous — Wed, 28 Feb 2018 15:50:23 +0000

Astronomers detect light from the Universe’s first stars Anonymous (not verified) Wed, 02/28/2018 - 08:50

Elizabeth Gibney

From Nature: Astronomers have for the first time spotted long-sought signals of light from the earliest stars ever to form in the Universe — around 180 million years after the Big Bang.

The signal is a fingerprint left on background radiation by hydrogen that absorbed some of this primordial light. The evidence hints that the gas that made up the early Universe was colder than predicted. This, physicists say, is a possible sign of dark matter’s influence. If confirmed, the discovery could mark the first time that dark matter has been detected through anything other than its gravitational effects.

“This is the first time we’ve seen any signal from this early in the Universe, aside from the afterglow of the Big Bang,” says Judd Bowman, an astronomer at Arizona State University in Tempe who led the work, which is published in Nature¹ on 28 February. “If it’s true, this is major news,” says Saleem Zaroubi, a cosmologist at the University of Groningen in the Netherlands. Other teams will need to confirm the signal but, so far, the finding seems to be robust, he says. “It’s very exciting stuff. This is a period in the Universe’s history we know very little about.” Read more...

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