Shortly after World War II and its stimulating role in the development of nuclear physics, seminal work showed that the stars were the furnaces in which elements heavier than the hydrogen, helium and lithium of the Big Bang and all their isotopes were distilled. However, this work had difficulty explaining the amounts of elements heavier than iron except through the inclusion of kilonovae. James-Webb has just consolidated the theory of the synthesis of these elements.
Unfortunately, Hubert Reeves has just left us. He used to say that we were stardust because the astrophysicist and atomic physicist that he was knew well that alchemy was at the origin of the elements of life, which gave rise to the nuclei carbon, oxygen, oxygen and nitrogen nitrogen, related to life and Death of stars took place. In fact, he had begun his doctoral studies at the time when the American astrophysicist of British origin Margaret Burbidge, her husband Geoffrey Burbidge and, accompanied by the cosmologist Fred Hoyle and the Nobel Prize winner in physics William Fowler, were the authors of an important article published in 1957 in which nothing less than the recipe followed by the universe to produce the chemical elements in the stars was laid out. Since then, the work has become known among nuclear astrophysicists as B2FH, after the initials of its authors.
Hubert Reeves himself had contributed to solving certain mysteries about the origin of the light elements that the B2FH article left unsolved. There was another possibility: the detailed origin of elements heavier than iron, such as gold and platinum, whose production during supernova explosions was not responsible for the observed abundances.
We’ve had ideas ever since.
It was enough to carry out intensive bombardments of neutron fluxes on iron nuclei, which, through their capture and via radioactive beta-beta decay reactions that gave proton protons, made it possible to obtain there such heavy elements as uranium and various isotopes, including those of iron . We are talking about the addition of neutrons through a fast process (r-process in English), but this process can be slow (s-process, s for slow).
How do you create this flux of neutrons? Of course with collisions of neutron stars, which should lead to so-called kilonovae, i.e. not as strong as supernovae. Kilonovae also emit gravitational waves and usually appear in the form of short gamma ray bursts, those incredibly powerful flashes of gamma photon photons.
The saga of the discovery of GW170817. To get a reasonably accurate French translation, click on the white rectangle at the bottom right. English subtitles should then appear. Then click on the nut to the right of the rectangle, then click on “Subtitles” and finally “Auto-translate”. Select “French”. © Science vs. Cinema
Kilonovae, gamma and gravity sources
In fact, on August 17, 2017, a gamma ray burst (GRB in English) designated SGRB170817A was discovered and located on the dome of the sky in association with the source of gravitational waves discovered by LigoLigo and Virgo: GW170817. The gravitational signal and others in the electromagnetic band confirmed that it was a collision of neutron stars, accompanied by the kilonova phenomenon. In this case, it is estimated that around a hundred times the Earth’s mass of gold nuclei would have been synthesized through the tremendous flux of released neutrons.
The James Webb Space Telescope (JWST) allows us to go a step further in our search for the origin of heavy elements, as has just been demonstrated in a paper published in Nature, and an open access version of which can be found on arXiv.
The discovery was made by the JWST focusing its near-infrared gaze on the gamma-ray burst GRB 230307A, identified by NASA’s Fermi orbiting gamma-ray telescopes and Neil Gehrel’s SwiftSwift. It is the second brightest gamma-ray burst observed in more than 50 years, about 1,000 times brighter than a typical gamma-ray burst observed by Fermi.
A nomadic intergalactic binary system?
Associated with this, James-Webb found the spectral trace of the element telluretellurium, which is the chemical element with atomic number 52 and the symbol Te in Mendeleyev’s table. Iron is the chemical element with atomic number 26, symbol Fe and is significantly lighter than tellurium. The spectral signature of Te, like other elements, is a kind of barcode with absorption lines in a light spectrum or, conversely, emission lines. This code is observed in laboratories on Earth and allows the presence of elements to be extrapolated without having to travel light years to perform chemical analysis on site.
Thus, GRB 230307A was formed by a collision of neutron stars and we thus find new direct evidence for the formation of elements heavier than iron by a kilonova. We already had similar evidence with strontium.
As a bonus, James-Webb helped determine that before the collision, the binary system of neutron stars must have originated in a galaxy from which it was ejected during the formation of the neutron stars themselves. SupernovaSupernova explosions of neutron star progenitor stars can be asymmetrical, which can lead to a rocket propulsion effect.
The binary star system would then have traveled approximately the diameter of the Milky Way before merging several hundred million years later.