Description
The Dark energy Spectroscopic Instrument (DESI) is measuring spectra of millions of distant galaxies and
quasars over a five-year period that started in spring 2021. A 3D map of the universe is built from the observations
and statistical methods applied to this map allows to place strong constraints on the underlying cosmological
Model. The main probe used in the data analysis is the baryonic acoustic oscillation that induces a characteristic
distance of separation between galaxies. This distance is measured across cosmic history and provides a measurement
of the history of the universe expansion. I will present the results based on the first three years of observations and
their impact on cosmology and in particular on the nature of dark energy and on the sum of neutrino masses.
