Dark energy is a form of energy that exerts a negative, repulsive pressure, behaving like the opposite of gravity. It has been hypothesised to account for the observational properties of distant type Ia supernovae, which show the universe going through an accelerated period of expansion. Like dark matter, dark energy is not directly observed, but rather inferred from observations of gravitational interactions between astronomical objects.
Dark energy makes up 72% of the total mass-energy density of the universe. The other dominant contributor is dark matter, and a small amount is due to atoms or baryonic matter.
- Dark energy survey internal consistency tests of the joint cosmological probes analysis with posterior predictive distributions. Monthly Notices of the Royal Astronomical Society, Volume 503, Issue 2, May 2021, Pages 2688–2705, https://doi.org/10.1093/mnras/stab526