The birth cycle of stars from clouds of matter constantly enriched with heavy elements synthesized by stars before dying in supernovae leads to the chemical evolution of galaxies. The James Webb measurement has just made it possible to estimate oxygen abundance in galaxies less than two billion years after the Big Bang, and it makes it possible to imagine worlds comparable to Earth sooner than previously thought.
When radioactivity was discovered at the end of the 19th century, nothing was known about the atom and chemists had given up on the idea that one element could be converted into another, in this case lead into gold. But in the wake of Pierre and Marie Curie, the New Zealand physicist and chemist Ernest Rutherford demonstrated that radioactivity was accompanied by the decay of chemical elements, which earned him the Nobel Prize in Chemistry in 1908.
A core chemistry will develop around the conversion of elements, which will lead to brilliant developments in astrophysics after the Second World War. Then it becomes possible to first understand how the stars behave like thermonuclear alchemical furnaces, capable of nucleosynthesis of the elements up to iron from isotopes of hydrogen, helium, helium and lithium, lithium and lithium, produced by the original nucleosynthesis were created during the Big Bang.
The origin of chemical elements – Part 1. By Nicolas Prantzos, CNRS, Institute of Astrophysics of Paris. A video of the AstrobioEducation learning course. © French Society of Exobiology
Stellar nucleosynthesis leading to the formation of galaxies
The late Hubert Reeves, who often spoke about stellar nucleosynthesis and the birth of the observable universe, had begun his scientific career precisely in the 1950s, at the height of the boom in nuclear astrophysics marked by an important 1957 paper, which revealed nothing less than the recipe followed by the universe to produce the chemical elements in the stars. The paper has since become known among astrophysicists and nuclear physicists as B2FH, after the initials of its authors, British astrophysicist Margaret Burbidge and her husband Geoffrey Burbidge, along with Fred Hoyle and Nobel Prize winner in physics William Fowler.
We now know that the cosmos arose without nuclei of oxygen, carbon, carbon and nitrogennitrogen, and without iron, magnesium, magnesium, silicon, sodium, sodium and aluminumaluminum. These cores form in the hearts of stars, which they launch into the interstellar medium through the explosion of supernovae in clouds of matter that, through gravitational collapse, produce new stars, stars that we now know will largely surround themselves with a protoplanetary diskprotoplanetary disk in which planets are born. Some will be rocky like Earth and based on silicates. Silicates, and carbon, nitrogen and oxygen compounds may have sometimes given rise to life forms similar to those we know on Earth.
The origin of chemical elements – Part 2. © Société Française d'Exobiologie
Stars form in galaxies and cause them to evolve chemically. Therefore, it is important for exobiologists who want to understand the origins of life in the observable cosmos to figure out when enough oxygen nuclei arose to make the emergence of life possible.
The James Webb Space Telescope has just provided some answers by more accurately measuring the amount of oxygen present in the stars of galaxies in the past, a team of researchers led by Japan's Kimihiko Nakajima of the National Astronomical Observatory of Japan (NAOJ) explains in an article that can be found in open access on arXiv.
Galaxies that are just as oxygen-rich as those we have today at the beginning of the cosmos
Professor Masami Ouchi, a member of the research team behind this article, explains in a press release from the Cosmic Ray Research Institute (cosmic rays) at the University of Tokyo that “the process of producing and storing oxygen in galaxies has long fascinated scientists.” The discovery A rapid increase in oxygen abundance in the early universe around 13.1 to 13.3 billion years ago suggests that life in the universe may have emerged earlier than “we previously thought.”
The standard cosmological model, based on data from the Planck mission, tells us that the observable cosmos is about 13.8 billion years old. Before James-Webb, we could barely measure oxygen levels in galaxies younger than 2 billion years.
But the JWST allowed Japanese researchers to reach further into the past with its near-infrared spectrograph (NIRSpecNIRSpec) by determining the content of oxygen nuclei in 138 galaxies.
They found that between 500 and 700 million years after the Big Bang, the abundances were half those observed in younger galaxies and were then comparable. Therefore, there was a rapid and early evolution in the chemical composition of galaxies, which made it possible to imagine planetary systems as oxygen-rich as ours as early as 700 million years after the Big Bang.
Are we alone in the Universe? Maybe you've asked yourself the question before… We find answers in films, literature or science fiction comics and our imaginations are populated by alien creatures! But what does science say about this? The AstrobioEducation website invites you to discover exobiology, an interdisciplinary science whose aim is to study the origin of life and its research elsewhere in the universe. On an educational journey divided into 12 stages, researchers from various disciplines will help you understand how science works to answer the fascinating questions about the origin of life and its research elsewhere than on Earth. © French Society of Exobiology