Detection of signals related to the first stars of the Universe

AFP

AFP

Wednesday, 28 February 2018 13:09

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Wednesday, 28 February 2018 13:12

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PARIS | astronomers have detected for the first time signals related to the appearance of the first star there was 13.6 billion years ago, shortly after the birth of the Universe, according to a study that has sparked a Wednesday, the excitement of the scientific community.

The author of this feat ? A small radio telescope installed in Australia, in which the antenna has the width of a refrigerator.

However, the discovery, announced in the journal Nature, has yet to be confirmed by other teams and other more powerful instruments, such as the radio telescope SKA (Square Kilometre Array), is currently under construction in Australia.

The community of astrophysicists has been surprised by the intensity of the observed signals, because it suggests that the Universe cooled more quickly than we thought.

This could lead to a review of the cosmological models, and perhaps allow them to better understand the mysterious dark matter is invisible to telescopes, but which made up more than a quarter of the Universe.

“Detection seeming of the signature of the first stars in the Universe will be a revolutionary discovery if it stands up to the weather,” says Brian Schmidt, Nobel prize for physics in 2011, who entrusts his “excitement”.

“It is the discovery astronomical the more important since the detection of gravitational waves in 2015,” says Karl Glazebrook, of the University of technology, Swinburne in Australia.

Other astrophysicists are more cautious. “We must remain very careful to the moment”, said to AFP Benoit Semelin (Observatoire de Paris. “But if the observation is confirmed, it is a major discovery, because it would imply changes in the model on the birth of the Universe”, he adds.

The discovery is the result of a work started there twelve years ago by a team led by astronomer Judd Bowman, of the University of State of Arizona (ASU).

Noise of the wings of a hummingbird

“It was a real technical challenge” to detect this signal which shows that the stars were already active in approximately 180 million years after the Big Bang, is Peter Kurczynski, from the National Science Foundation (NSF), which funded the study.

Multiple radio waves are emitted in particular by the milky Way, our galaxy. “The sources of noise can be 10,000 times stronger than the signal. This means finding oneself in the middle of a hurricane, and try to hear the noise of the wings of a hummingbird,” he says.

In spite of everything, “these researchers with their small radio antenna in the desert have seen farther than space telescopes more powerful”, “opening a new window into the young Universe”, he adds.

The study also revealed that the gas in the Universe, at the time of the appearance of the first stars, was much colder than expected. It would have been 3 degrees Kelvin (-270 degrees Celsius).

The astrophysicist Rennan Barkana, Tel Aviv University, to advance an explanation in another study, also published in Nature.

According to him, the ordinary matter would be input in interaction with dark matter and he would have surrendered gradually of energy.

“If the idea of Barkana is confirmed, we will have learned something new and fundamental about this mysterious dark matter”, stresses Judd Bowman.

Dark matter accounts for 26.8% of the Universe. The latter is also composed of ordinary matter (4.9%) and dark energy (68.3 per cent), according to data from the Planck satellite published in 2013.

The dark matter can absorb, reflect or emit light, which makes it extremely difficult to detect. Scientists have inferred its existence from the gravitational effect it seems to have on visible matter.

But for Benoît Semelin, the assumption of Rennan Barkana seems to be “speculative” for the moment.