2023-07-22 17:20:08
It is known that in the depths of the Earth, high pressures and temperatures lead to the formation of diamonds from carbon. It must be the same with the carbonaceous dust produced by stars at the end of their life in the red giant phase as well as with the explosions of supernovae. In fact, for decades, nanodiamonds have been discovered in presolar grains, older than the Solar System and which can be found in the oldest carbonaceous meteorites.
They are objects containing a few thousand carbon atoms forming a characteristic crystalline structure and gathered in a volume of a few nanometers, that is to say billionths of a meter in diameter. They can be obtained as the milky residue of a fragment of a carbonaceous meteorite dissolved in acid.
Today, and as explained in an article published in Natureit is thought that the infrared signature of these nanodiamonds is probably observed in galaxies as revealed by the James-Webb Space Telescope about a billion years after the Big Bang at most.
Galaxies that grew faster than theory predicts?
Joris Witstok of the University of Cambridge, one of the main astrophysicists behind this discovery, explains: Carbon-rich dust grains may be particularly good at absorbing ultraviolet light with a wavelength of around 217.5 nanometers, which we have for the first time directly observed in the spectra of very old galaxies. Let us recall in passing that the James-Webb (JWST) sees in the infrared spectra whose light has been shifted towards the red by the expansion of the Universe, for example lines in the ultraviolet at the origin.
Also in the same ESA press release, his colleague Renske Smit, a member of the team at John Moores University in Liverpool, UK, adds: “ This discovery implies that the infant galaxies of the early Universe grew much faster than we had expected. Webb shows us a complexity of the early birthplaces of stars (and planets) that models have yet to explain ».
Once again, Hubble’s successor gives us indications showing that the galaxies have evolved faster than we supposed for a few decades, which perhaps suggests that the Standard Cosmological Model needs to be revised, for example by replacing the presence of dark matter with a modification of the laws of gravity within the framework of the Mond theory, although it is still too early to conclude that this model is not in fact able to predict the observations made with the James-Webb.
Incidentally, despite the buzz recent and very exaggerated which infuriates the community of cosmologists, we have no serious reason to think that the observable Universe is older than 13.8 billion years and is in particular 26.7 billion years old, as proposed by the physicist Rajendra Gupta by multiplying the epicycles. In particular, we have known for decades that the theory of “tired” light – which proposed to explain spectral redshifts without involving the expansion of the observable cosmos – leads to at least three predictions which are refuted by observations at around 10 sigma, to use the jargon of physicists (see what the cosmologist Ned Wright has been saying for a long time). A refuted result at 5 sigma already means that there is only a one in a million chance that the rebuttal is wrong, a considerably lower chance even with 10 sigma.
This gives an idea of the little credible, although logically possible, acrobatics that must be multiplied to obtain an age of 26.7 billion years. In particular, it is necessary to assume that certain fundamental constants of physics vary over time when there are already very strong constraints on these possible variations, and also to take into account the dating with chronometers of star clusters and the abundances of certain nuclei in the Milky Way which are all incompatible in first approximation with a Universe really older than 13.8 billion years.
Nanodiamonds or polycyclic aromatic hydrocarbons?
But back to the detection of nanodiamonds. In fact, the signature detected by the James-Webb could very well be interpreted in the case of galaxies observed such as they were only a few billion years ago by the abundant presence of carbonaceous molecules, which are called polycyclic aromatic hydrocarbons cousins of benzene molecules ( polycyclic aromatic hydrocarbons or PAH, in English). But in galaxies about 600 million years old after the Big Bang, such as those that have therefore been observed as part of the JWST Advanced Deep Extragalactic Survey (Jades), this hypothesis is not credible according to astrochemists who therefore deduce that nanodiamonds are very probably observed.
If so, ” This discovery was made possible by the unparalleled improvement in the sensitivity of near-infrared spectroscopy provided by Webb, and in particular its near-infrared spectrograph (NIRSpec). The increase in sensitivity provided by Webb is equivalent, in the visible, to the instantaneous upgrade of Galileo’s 37 millimeter telescope by the Very Large Telescope 8-meter ESO “, explains Roberto Maiolino, member of the team of the University of Cambridge and theUniversity College London behind the discovery of nanodiamonds.
« We plan to work more with theorists who model the production and growth of dust in galaxies. This will shed light on the origin of dust and heavy elements in the early Universe. added Irene Shivaei, a member of the University of Arizona team, Astrobiology Center (CAB).
Nanodiamonds and meteorites. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © thebrainscoop
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