Our universe is full of many mysteries that continue to surprise scientists. Recent observations made by the James Webb Space Telescope have highlighted certain completely new aspects linked to primitive galaxies.
According to the conclusions of a study published on September 21 in Nature Astronomysuch galaxies – whose chemistry is very sparse – seem to deviate from the theoretical relationships established between chemical composition, stellar mass and star formation.
This new Danish work – led by Kasper Elm Heintz of the Cosmic Dawn Center in Copenhagen – is discussed in detail in a press release (accessible HERE) spotted by the site Trust My Science. They suggest a constant supply of new gas. By diluting the heavy elements, said gas would help shape a unique chemical composition.
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Galactic formation and evolution rethought?
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Until now, observations led scientists to say that the galaxies of the last 12 billion years (which corresponds to 5/6th of the age of the universe) have existed in a form of equilibrium. There seems, in fact, to exist a fundamental relationship between the quantity of heavy elements created [des éléments plus lourds que l’hélium et l’hydrogène] and the number of stars formed.
Because the Universe was – originally – exclusively made up of much lighter elements, such a relationship seems most logical, observes the Trust My Science site. Whether it is oxygen, carbon or even iron, the heavier elements were created much later, by the stars.
An observation which suggests that the first galaxies should not have been “polluted” by heavy elements.
Until recently, however, it has never been possible to go back to such an ancient period. The technology of this space telescope therefore contributes to improving the knowledge of experts.
Research carried out by the team supervised by Kasper Elm Heintz (which focused on galaxies formed shortly after the Big Bang) revealed surprising chemical and physical properties. So much so that specialists may be forced to rethink current models regarding galactic formation and evolution…
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Lower amounts of heavy elements
Generally speaking, the more massive the galaxy, the heavier the elements. However, such a link has been called into question by recent observations. In the press release, Kasper Elm Heintz explained that he and his colleagues had “analyzed the light of sixteen of the first galaxies”.
Scientists have found that they “contained fewer heavy elements than would be expected given their stellar masses and the number of new stars they produced”.
Another observation, which greatly surprised experts, is linked to the reduced production of heavy elements in ancient galaxies. The lessons that specialists have learned diverge from the predictions made in the past. Predictions that were based on knowledge gained about later formed galaxies.
More precisely, it turns out that such galaxies contained, on average, four times fewer heavy elements than the “older” Universe.
The results highlighted by this Danish team contrast with the current model, which considers that galaxies have continued to evolve following a certain form of equilibrium.
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A singularity due to the continuous reception of new gas
“It was as if the galaxies followed a rule, but, surprisingly, this cosmic rule seems to have undergone a rewrite during the infancy of the universe”reacted Claudia Lagos, associate professor at the University of Western Australia and cited by Trust My Science.
A singularity that the specialist justified by arguing that it was due to the continuous reception of new gas which comes from the cosmic environment. In galaxies, such a constant flow will dilute the heavy elements present. The consequence is a reduced concentration of these elements, compared to what is observed in more mature galaxies.
Claudia Lagos also points out that such dilution of heavy elements is crucial to better understand the evolution (and nature) of primitive galaxies. In the structure of galaxies and the formation of stars, heavy elements play a key role. Their presence, when reduced, suggests distinct formation and evolution processes for ancient galaxies.
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