In a laboratory they were reproduced the first reactions in space In conditions similar to those of the primordial universe, before the birth of the stars, noting many discrepancies with current hypotheses. A research group led by Max Planck Institute (Germany) could therefore rewrite the theories on the origin of the universe.
As scientists explain, the Heh⁺ ion was the first molecule to form in the primordial universe, before the birth of the stars. And now, for the first time in history, the researchers have studied Heh’s reactions+ With hydrogen atoms in conditions similar to those of that beginning of the universe. And it doesn’t seem to have gone as it has always been thought so far.
What we know about the origin of the universe
Immediately after the big Bangoccurred around 13.8 billion years ago, the universe was dominated by unimaginably high temperatures and density. However, after a few seconds, it had cooled enough to allow the formation of the first elements, mainly hydrogen and helium.
At this point, these were still completely ionized (i.e. the atoms were not neutral), since it took it Almost 380,000 years so that the temperature in the universe dropped enough to allow the formation of neutral atoms through recombination with free electrons. This opened the way to First chemical reactions.
The oldest molecule existing is Elio’s hydrucious ion (Heh+), formed by an atom of neutral helium and an ionized hydrogen nucleus: this ion has marked the beginning of a chain reaction that led to Molecular hydrogen formation (H2), by far the most common molecule in the cosmos.
However, several hundred millions of years passed before the birth of the first stars, but during this primordial phase simple molecules such as Heh+ and h2 They were essential for their training.
In fact, so that the cloud of gas in contrasting a liability protostella to the point where nuclear fusion can start, the heat must be dissipated, and this occurs through collisions that excite atoms and molecules, which in turn emit this energy in the form of photons.
Below about 10,000 degrees Celsius, however, this process becomes ineffective for hydrogen atoms, while further cooling can only take place through molecules and ions capable of emitting further energy through rotation and vibration, and among these Heh+ It is particularly effective at these low temperatures, and for this long, considered a potentially important candidate for cooling in the formation of the first stars.
Consequently, the concentration of Elio’s hydrucious ions in the universe It can have a significant impact on the effectiveness of primordial stellar formation. During this period, in fact, collisions with free hydrogen atoms represented an important degradation path for Heh+forming an atom of neutral helium and one ion h2+. These subsequently reacted with another H atom to form a neutral H₂ and a proton molecule, leading to Molecular hydrogen formation.
What the researchers have now discovered
The researchers of Max-Planck-Institut Für Kernphysik Of Heidelberg they succeeded for the first time a successfully recreate this reaction in conditions similar to those of the primordial universe. They studied in particular the reaction of the Heh ion+ With deuterio (D), an atom of hydrogen with an extra neuron (therefore called isotope), so that the reaction led to the formation of the HD ion+ instead of h2+next to the atom of Elio Neutro.
The experiment was conducted at the Cryogenic Storage Ring (CSR), a unique tool in the world for the study of molecular and atomic reactions in conditions similar to spatial ones. For this purpose, the heh ions+ They were stored in the instrument and superimposed on a bundle of neutral deuterio atoms.
By regulating the relative speeds of the two bundles of particles, scientists have been able to study how the collision speed varies according to the collision energyin turn directly related to temperature. And they discovered that, contrary to the previous forecasts, the speed of this reaction does not slow down with the decrease in temperature, but remains almost constant.
Previous theories involved a significant decrease in the probability of reaction at low temperatures, but we were unable to verify it in the experiment or in the new theoretical calculations of our colleagues – explains Holger Kreckel, who led the study – Heh’s reactions+ With neutral and deuterio hydrogen they seem to have been much more important for chemistry in the primordial universe of what has been previously hypothesized
This observation is consistent with the results of a group of theoretical physicists led by Yohann Scribanowhich identified a mistake in the calculations made previously for this reaction.
Since the concentrations of molecules like Heh+ and molecular hydrogen (h2 or HD) played an important role in the formation of the first stars, this result brings us closer to the solution of the mystery of their training
the authors conclude
In other words, while not contesting the big Bangthe researchers suggest doubts about the current theory of what happened immediately after, especially as regards the birth of the stars.
Are we therefore close to the solution? Too soon to say, but this research is certainly the ranks like a milestone on the road in the right direction.
The research was published on Astronomy & Astrophysics.
Sources: Max-Planck-Institut Für Kernphysik / Astronomy & Astrophysics
