Cosmology; detection of first light (Introduction)

by David Turell , Saturday, March 03, 2018, 18:42 (2457 days ago) @ David Turell

Light in the initial darkness came (by theory) with the first stars:

https://cosmosmagazine.com/space/first-light-the-signature-of-the-earliest-stars-detected

"The traces of the first daybreak in the universe have been detected by a small radio-telescope in Western Australia.

"Astronomers know that shortly after the Big Bang, 13.7 billion years ago, everything was dark. After its intensely energetic burst of expansion, the universe cooled. Gradually, in the ensuing eons, gravity pulled bits of matter together into clumps, then into larger bodies, until finally, around 180 million years after the process began, a critical mass was reached and the first stars ignited.

"As the light interacted with hydrogen gas, a signal was created. That signal has now been finally detected by a collaboration between Australian research organisation, the CSIRO, and Arizona State University in the US.

"The accepted models for predicting events in the very early universe suggest that when ultraviolet light produced by the first stars interacted with hydrogen gas, it would change how the gas absorbs radiation. This change was expected to show up as a dip in radiowaves coming from space at frequencies lower than 200 megahertz.

"In a paper published in the journal Nature, scientists led by Judd Bowman of Arizona State report the detection of such a dip around 78 megahertz, with a profile “largely consistent with expectations” for signals produced by early stars.

"There are, however, some significant differences between it and the predictions, Mainly, Bowman and colleagues reveal the amplitude of the signal is twice as strong as suggested in even the uppermost estimates.

"This, they write, may be because the primordial hydrogen was colder than expected, or the radiation temperature was hotter. The scientists suggest the best-fit explanation is cooling caused by interactions between dark matter and subatomic particles.

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“'This is one of the most technically challenging radio astronomy experiments ever attempted,” says MRO manager Antony Schinckel.

“'The lead authors include two of the best radio astronomy experimentalists in the world and they have gone to great lengths to design and calibrate their equipment in order to have convincing evidence for a real signal.”

"Schinckel describes the result as “an absolute triumph”.

"Other scientists have been equally effusive.

“'The apparent detection of the signature of the first stars in the universe will be a revolutionary discovery if it stands the tests of time,” says astrophysicist and Nobel laureate Brian Schmidt.

“'While the detection appears robust, it is an incredibly challenging measurement, and needs to be confirmed. The fact that the detection is much stronger than expected, and that can be easily explained, is particularly exciting.”

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"If the signal is confirmed by other experiments (which may happen soon),” he adds, “the implications for our understanding of the evolution of the universe and the nature of cosmic dark matter will be profound.'”

Comment: It is truly amazing how much can be predicted from the dawn of the universe deduced from observations made and understood today.