5000 eyes on the cosmos

Over the next five years, no less than 5000 optical fiber “eyes” will capture the light of millions of different celestial objects, mainly galaxies, but also quasars and some stars.

The Dark Energy Spectroscopic Instrument (DESI) has seen its “first light”, which means that its installation is almost complete and that it will be able to start as planned at the beginning of 2020 its gigantic cartography of the energy. sky.

The first scientific data are expected for 2021.


  • The mission is led by the American laboratory Lawrence Berkeley.
  • The instrument is installed on the Mayall telescope of the Kitt Peak Observatory, Arizona.
  • No less than 500 scientists from 75 organizations from 13 countries participate.

A deep look at the Universe

The main objective of this international effort is to scrutinize the sky to measure in detail the accelerated expansion of the Universe, but also to better understand the effects of dark energy.

More concretely, in the next five years, it will record the ultraviolet, visible, and infrared spectrum of more than 38 million objects, including 35 million galaxies and 2.4 quasars.

It was designed to automatically point to a list of preselected objects.

Thus, every 20 minutes, it will measure the spectrum of 5000 objects, five times more stars and twice as fast as the best current instruments.

It will detect their light and break it up into multiple wavelengths to determine their positions and distances from the Earth.

With all the information gathered, DESI will create the most detailed 3D map to date covering the Near Universe up to 11 billion light-years.

Mysterious energy

Measurements of the distances of objects will be compared to the predictions of the standard model of cosmology according to which the Universe is composed in part by what is called black energy .

It should be known that astrophysicists know very little about this energy, a mysterious element that constitutes about 68% of the mass-energy of the current Universe.

According to scientists, she would be responsible for accelerating the expansion of the Universe.

By looking at very different objects and at different times, we will be able to map the history of the Universe and understand its composition.

Nathalie Palanque-Delabrouille, French Atomic Energy and Alternative Energies Commission

“DENI represents a significant progress compared to the previous instruments by the number of objects measured,” explains Nathalie Palanque-Delabrouille.

As the light of each object takes a while to reach the Earth, the maps provided by DESI will provide access to the past evolution of the Universe at different times.

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