Einstein abandoned the constant in 1931 after Hubble's confirmation of the expanding universe. ... The cosmological constant Λ is the simplest possible explanation for dark energy, and is used in the current standard model of cosmology known as the ΛCDM model.

What is the status of the cosmological constant today?

Observational evidence for the accelerating universe is now very strong, with many different experiments covering vastly different timescales, length scales, and physical processes, all supporting the standard \LambdaCDM cosmological model, in which the universe is flat with an energy density made up of about 4% ...

Was Einstein correct about the cosmological constant?

Physics lore has it that Einstein later confessed that his introduction of the cosmological constant was perhaps his greatest blunder. In 1998, observations of distant supernovas showed the universe wasn't just expanding, but the expansion was speeding up. ... Yet this constant is not understood," Lombriser said.