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Glossary term: Fond diffus cosmologique (FDC ou CMB en anglais)

Description: Le fond diffus cosmologique (FDC ou CMB en anglais) est le rayonnement électromagnétique relique datant de l'époque où l'Univers avait environ 380 000 ans et est devenu transparent à la lumière. Il fournit des informations sur la composition, la géométrie (forme), l'évolution et le développement de la structure de l'Univers. L'Univers dense primitif était constitué d'une "soupe chaude" de particules libres (protons, neutrons, électrons) et de lumière (photons). Avant que le fond diffus cosmologique ne soit libéré et mesuré, l'interaction des photons avec les électrons libres empêchait la lumière de parcourir de longues distances. L'expansion et le refroidissement de l'Univers ont permis aux électrons libres de se combiner avec les protons pour former l'hydrogène atomique, et à la lumière de voyager à travers l'Univers. L'expansion a ensuite étiré la longueur d'onde de ces photons, ce qui les rend détectables aujourd'hui dans la région des micro-ondes du spectre électromagnétique.

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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

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This Cosmic Microwave Background Radiation map is an oval with many patches of different colors as well as finer granulation

Cosmic Microwave Background Radiation

Caption: This image is a representation of the Cosmic Microwave Background (CMB) Radiation created using data from the Planck satellite. The CMB is the glow left over from when the Universe was approximately 380,000 years old. The early Universe was hot and dense, so the photons from that era were high energy. Due to the expansion of the Universe over 13.8 billion years photons of ""light"" from the early Universe have been stretched to longer wavelengths and are detectable in millimetre wavelengths (microwave region of the electromagnetic spectrum). The ""mottled"" pattern in the image is referred to as anisotropies, and it represents very small temperature fluctuations. These fluctuations correspond to regions of slightly different densities, and are essentially the seeds for larger structure in the Universe e.g.: galaxies, galaxy clusters, and the very first stars. The data from the CMB allows various characteristics of the Universe to be derived, for example, composition, shape, age, and allows for certain predictions to be made about the future evolution of the Universe. The shape of the image is the result of a mapping projection, where the entire sky is mapped onto a single flat oval shape called Molleweide projection. The center of the Milky Way galaxy is located at the centre of the image.
Credit: ESA/Planck Collaboration credit link

License: CC-BY-SA-4.0 Creative Commons Attribution - Partage dans les Mêmes Conditions 4.0 International (CC BY-SA 4.0) icons

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