The exact density of dark energy, often represented by the symbol ΩΛ (Omega Lambda), is a subject of ongoing scientific research and investigation. Dark energy is a hypothetical form of energy that is thought to be responsible for the observed accelerated expansion of the universe.
Current observations indicate that dark energy contributes approximately 68% of the total energy density of the universe. This value is derived from measurements of the cosmic microwave background radiation, large-scale structure of the universe, and supernovae data.
However, expressing the density of dark energy in terms of its amount per cubic kilometer (km^3) is not a common practice in astrophysics or cosmology. The reason is that dark energy is believed to have a relatively constant energy density throughout space, meaning its density is the same regardless of the volume considered.
Instead, the density of dark energy is often expressed in terms of its density parameter, ΩΛ, which represents the fraction of the critical energy density of the universe that is attributed to dark energy. The value of ΩΛ is currently estimated to be around 0.68, indicating that dark energy constitutes about 68% of the total energy density of the universe.
It's important to note that our understanding of dark energy is still incomplete, and further research and observational data are needed to refine our knowledge of its properties and precise density.