Space and Physics
PUBLISHED
The Dark Energy Spectroscopic Instrument (DESI) has achieved its goal. Every single area of the sky that the collaboration set out to map has been mapped, and slightly ahead of its five-year target. DESI was set to gather data on 34 million galaxies and quasars. The final tally of the survey was 47 million galaxies and quasars, the largest high-resolution 3D map of the Universe ever assembled. The ultimate goal is to understand dark energy.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Dark energy is a crucial component that is expected to exist in the universe. A form of energy responsible for the accelerated expansion of the universe. We don't know what it is exactly, but since we have found that the cosmos is getting ever bigger, dark energy has been put forward as a cosmological constant, something that is always the same and found everywhere in the universe.
DESI is set to answer the question of dark energy by understanding how the universe has changed over the last 11 billion years. Analysis of data from the first three years of the survey suggests that the cosmological constant formulation may not be correct. Maybe dark energy is weakening over time. The data of the full five years might confirm those preliminary findings. The first analysis of that is expected in 2027, while data from the first three years continue to be reanalyzed and refined.
“DESI’s five-year survey has been spectacularly successful,” Michael Levi, DESI director and a scientist at Berkeley Lab, said in a statement. “The instrument performed better than anticipated. The results have been incredibly exciting. And the size and scope of the map and how quickly we’ve been able to execute is phenomenal. We’re going to celebrate completion of the original survey and then get started on the work of churning through the data, because we’re all curious about what new surprises are waiting for us.”
DESI will continue to work through 2028, adding about 20 percent to the current map. It will include areas of the sky that are more complicated to observe, such as near the Milky Way’s Zone of Avoidance, as well as lower on the horizon, having to deal with more of the Earth’s atmosphere.
It will also observe fainter and more distant luminous red galaxies in both the new areas and the areas that have already been mapped. On top of that, DESI will study nearby dwarf galaxies, stellar streams, and stars around the Milky Way. It has already observed more than 20 million nearby stars.
“We’ve built a remarkable piece of equipment that met all our expectations and then some,” Levi said. “Now we’re pushing beyond our original plan. We don’t know what we’ll find, but we think it’ll be pretty exciting.”
