Cosmic voids and their evolution

In the vastness of the universe, beyond the twinkling of galaxies, lie enormous regions practically devoid of visible matter, the cosmic voids. These areas, true depressions in the large-scale structure of the cosmos, offer a striking contrast to the dense filaments and galactic clusters that compose the cosmic web. Their characteristics, formation, and role in … Read more

Detailed primordial nucleosynthesis

Primordial nucleosynthesis, a fundamental phenomenon marking the chemical genesis of the universe, unfolded during the very first minutes following the Big Bang. It was during this intense phase that the first light atomic nuclei appeared, giving birth to elements that will constitute the fundamental building blocks of cosmic matter. This crucial step conditioned the cosmic … Read more

The reionisation of the primordial universe

The reionization of the primordial universe is a crucial step in cosmic evolution that occurs after the Dark Age, a period during which the cosmic atmosphere was dominated by opaque neutral hydrogen. This phenomenon reflects the gradual transition of this dark universe to a lit and ionized environment through the emergence of the first stars … Read more

The entropy of black holes and information

Since the 1970s, the study of black holes has profoundly transformed the understanding of entropy, a fundamental concept in thermodynamics, by tying it to the most mysterious astrophysical objects in the universe. The revelation that these strange regions of spacetime can possess entropy, measuring the amount of information they contain, has not only opened new … Read more

The physics of hypothetical wormholes

Wormholes remain one of the most fascinating and enigmatic concepts of modern theoretical physics, resonating with both the strings of science and those of science fiction. These hypothetical structures represent shortcuts within the fabric of space-time, proposing the captivating idea that the universe could be traversed almost instantaneously through these cosmic tunnels. Anchored in the … Read more

Liquid water in the outer solar system

The presence of liquid water in the outer solar system generates considerable scientific interest, particularly due to its potential link to life beyond Earth. While most visible liquid water is confined to our planet, recent discoveries suggest that this vital element also exists in other forms, primarily as ice, on several moons and distant celestial … Read more

The role of cosmic rays in the universe

Le rôle des rayons cosmiques dans l'univers

IN BRIEF Cosmic rays: high-energy subatomic particles coming from space. Messengers of violent events in the universe. Composed mainly of protons and atomic nuclei. Create large showers of secondary particles upon their manifestation. Constantly bombard the Earth and impact our atmosphere. Represent one of the greatest dangers for astronauts in space exploration. Play a crucial … Read more

The study of variable stars in astrophysics

L’étude des étoiles variables en astrophysique

IN SHORT Variable stars: celestial bodies that show variations in brightness. Two main types: Cepheids and RR Lyrae stars. Periodic volume variations affecting brightness and spectrum. Essential for estimating astronomical distances. Constantly increasing cataloging, with a variety of characteristics. Used to determine stellar dynamics. Long-period variable stars: red supergiants with marked brightness variations. Interest in … Read more

Chemistry in the Universe: The Basics of Life

La chimie dans l'univers : les bases de la vie

IN BRIEF Primordial nucleosynthesis: the initial formation of elements after the Big Bang. Origin of matter: explained by the Big Bang model. Carbon chemistry: the foundation of life on Earth with sugar, proteins, lipids. First molecule: the helium hydride ion (HeH+) could be the very first formed element. Complexification of atoms: evolution of hydrogen atoms … Read more

Relativistic jets and their mysteries

Les jets relativistes et leurs mystères

IN BRIEF Relativistic jets: ejections of matter at speeds close to that of light. Source: originating from accretion disks around black holes. Observation: monitoring a black hole for 15 years by an international team of astronomers. Power: the most powerful phenomena observed in astrophysics. Structure: jets maintain a narrow structure over vast distances. Rotation: the … Read more