The James Webb Space Telescope (JWST) continues to surprise astronomers. In just two years, it has revealed extremely distant, yet above all incredibly luminous galaxies that challenge our current theories.
These galaxies, observed shortly after the Big Bang, shine much more brightly than we would have expected for this period. Yet, our cosmological models predicted that star formation at this time should have been more gradual.
Artist's rendering of the James Webb Space Telescope.
Credit: NASA
These discoveries are leading scientists to reconsider some hypotheses about galaxy formation. Indeed, the luminosity of these objects could be linked to much more intense star formation than anticipated. The JWST uses spectroscopy to study these distant galaxies. This method allows the analysis of light to determine the properties of stars and gas in these systems. Through it, researchers can uncover the secrets of the early universe.
The standard cosmological model, called ΛCDM, includes three major components: ordinary matter, cold dark matter, and dark energy. This framework largely explains the formation of the galaxies we observe today.
However, the presence of galaxies this bright and this rapidly formed challenges some aspects of this model. Adjustments in the way gas transforms into stars might be necessary. Recent theories even suggest that an "early dark energy" could have played a role in this accelerated formation. This hypothesis could explain both the rapid growth of galaxies and other mysteries like the "Hubble tension."
For now, these galaxies do not "break" the Universe, but they open the door to new research. The JWST continues to provide valuable data, and astronomers expect even more revelations about our cosmic origins.
What is dark matter?
Dark matter is a type of invisible matter that cannot be directly detected with current instruments. It neither emits, absorbs, nor reflects light, making it undetectable by conventional observational methods.
Scientists know it exists thanks to its gravitational effects. It accounts for about 85% of the matter in the Universe and plays a key role in the formation and evolution of galaxies by exerting a gravitational force on visible matter.
Dark matter remains one of the greatest mysteries of modern cosmology.
What is dark energy?
Dark energy is a form of energy that makes up about 68% of the Universe. It is responsible for the acceleration of the Universe's expansion, a phenomenon discovered in the 1990s through the observation of distant supernovae.
Unlike dark matter, dark energy does not interact with gravity in the traditional way. Instead, it acts more like a repulsive force that causes the Universe to expand at an increasing rate.
Although dark energy is a fundamental concept in the current cosmological model, its exact nature remains largely misunderstood.