Relic of the Big Bang discovered

Astronomers discover primordial hydrogen cloud with hardly heavy elements

Ancient Gas: This simulation shows cosmic gas filaments in which clouds of primordial gas from the time directly after the Big Bang are hidden. © TNG Collaboration
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Surprisingly original: astronomers have discovered a gas cloud that could have come from the time just after the Big Bang. Because it contains virtually no heavier elements - and thus no traces of the first stars, as shown by spectral analyzes. This cloud of hydrogen could therefore be one of only three previously known relics from the earliest era of the universe.

With the Big Bang initially only the lightest elements hydrogen, helium and lithium were formed. All other types of atoms were first formed by nuclear fusion inside the first, short-lived stars. Through their supernova explosions, the heavy elements - astronomers speak of "metals" - spread throughout the cosmos. Gas clouds without this metallic "contamination" are therefore hardly found today. Astronomers have so far discovered only two relics from the very earliest of the cosmos, another gas cloud could at least come from the time of the first stars.

Manhunt with Quasarhilfe

Another relic from the time of the Big Bang has now been discovered by Frederick Robert of the Swinbourne University of Technology and his colleagues. For their study, they had specifically searched for distant hydrogen clouds that contain no or hardly heavy elements. "The first two clouds of this kind were coincidental, but we wanted to see if they were not just the tip of an iceberg, " says co-author John O'Meara of St. Michael's College in England.

For their study, astronomers searched for distant quasars whose light falls through hydrogen clouds in front of them. Using the highly sensitive HIRES spectrograph of the Keck Observatory in Hawaii, they then analyzed the elemental signatures left by the gas in the light shining through the cloud. Eight such so-called Lyman-Limit systems (LLS) screened them in this way.

Spectrum without metal lines

And indeed: In one of the hydrogen clouds, the researchers found what they were looking for: "One of these gas clouds, LLS1723, appeared to be completely free of metal lines in the HIRES spectrum, " the scientists report. The cloud was similarly metal poor as the two well-known relics of the Big Bang - and could therefore come from a similarly early time, as the astronomers explain. display

"This gas cloud seems completely original: Even 1.5 billion years after the Big Bang, it is not polluted by stardust, " says Robert. "If it contains any heavy elements at all, they must account for less than a ten-thousandth of the metals in the sun. This is extremely low and the obvious explanation is that this is a true relic of the Big Bang. "

"Fossil" of the Big Bang

According to astronomers, LLS1723 could come from the very earliest nursery in the universe from a time before the first stars were born. "Metal-free clouds like LLS1723 could consist of primordial, intergalactic gas that has survived all the confusion of the early universe and never been contaminated by stars, " the researchers said. Then these clouds would be exciting fossils of the Big Bang, which could provide new insights into this early period of the cosmos.

On the basis of the previous data, however, it can not be ruled out that this gas cloud arose a little later - with the first generation of stars. Because even these were still relatively poor in heavy elements, so that the impurities would be extremely low by their Explosionsstr mmer, as Robert and his colleagues explain. In further investigations, you now want to find out more about these unusually "clean" gas clouds and also look for other representatives of these Lyman-Limit systems. (Monthly Notices of the Royal Astronomical Society, in press)

Source: WMKeck Observatory

- Nadja Podbregar