What have dark energy surveys revealed about the fate of the universe?

The answer

The Dark Energy Survey (DES), using the 570-megapixel Dark Energy Camera on the 4-meter Blanco telescope in Chile, completed its six-year observing campaign in 2019, cataloging over 300 million galaxies across one-eighth of the sky. Final results released in 2023-2024 confirmed that dark energy - comprising approximately 68% of the universe's energy content - behaves consistently with Einstein's cosmological constant (w = -1). However, the Dark Energy Spectroscopic Instrument (DESI), which began releasing results in 2024 from its survey of 40 million galaxies and quasars, found preliminary hints that dark energy's strength may be changing over time. If confirmed, this would rule out a simple cosmological constant and suggest dark energy is a dynamic field. The Euclid space telescope, launched in July 2023 by ESA, is mapping the 3D distribution of 2 billion galaxies to further constrain dark energy models.