1) An extensive area with a fairly level surface raised sharply above adjacent land.
From Fr. plateau, from O.Fr. platel "flat piece of metal, wood, etc.," diminutive of plat "flat surface or thing," → plate.
Taxtâl, from taxt "flat;" Mid.Pers. taxtag "tablet, plank, (chess)board" + -âl, → -al.
Fr.: plateau de Sachs-Wolfe
An almost horizontal region in the → CMB angular power spectrum belonging to a → multipole index 10 ≤ l ≤ 100. This feature is due to the → Sachs-Wolfe effect.
→ Sachs-Wolfe effect; → plateau.
Fr.: plateau des Spite
The observation that the abundance of → lithium (7Li) in metal-poor stars is constant regardless of the → effective temperature (> 5500 K) and the → metallicity ([Fe/H] < -2). The Spite plateau is currently interpreted as evidence that the Li observed in → halo population stars is → primordial. Since its discovery, the Spite plateau has been subject to numerous investigations, increasing the number of stars with Li measurements and extending the sample to include ever lower metallicities. Important issues are the existence or not of a significant scatter along the plateau, and the existence or not of atomic diffusion and mixing with deeper stellar zones where Li can be burnt, producing an offset with respect to the → Big Bang → nucleosynthesis abundance. Several recent studies have shown that the Spite plateau exhibits very little, if any, dispersion. There is, however, a discrepancy between recent results and that derived from Big Bang nucleosynthesis, based on the cosmological parameters constrained by the → WMAP measurements.
Named after François and Monique Spite, French astronomers, Paris Observatory, who first discovered this relation (1982, A&A 115, 357); → plateau.