An international team led by Prof. Gong-Bo Zhao of National Astronomical Observatories of China (NAOC) revealed an evidence of dynamical dark energy using the latest astronomical observations. This discovery suggests that the nature of dark energy may not be the cosmological constant introduced by Albert Einstein 100 years ago, which is crucial for the study of dark energy.

This work has been published online in the world-renowned science journal of Nature Astronomy on August 28th, 2017 (Beijing time), with a News & Views article written by a world expert on cosmology published on September 5th(https://www.nature.com/articles/s41550-017-0236-8).

Revealing the nature of dark energy is one of key goals of modern sciences. The physical property of dark energy is represented by its Equation of State (EoS), which is the ratio of pressure and energy density of dark energy. In the traditional LCDM model, dark energy is essentially the cosmological constant, i.e., the vacuum energy, with a constant EoS of -1.In this model, dark energy has no dynamical features.

In 2016, a team within the SDSS-III (BOSS) collaboration led by Prof. Gong-Bo Zhao performed a successful measurement of the Baryonic Acoustic Oscillations (BAO) at multiple cosmic epochs with a high precision (Zhao et al., 2017, MNRAS, 466, 762).

Based on this measurement and a method developed by Zhao for dark energy studies, the Zhao team found an evidence of dynamical dark energy at a significance level of 3.5 sigma. This suggests that the nature of dark energy may not be the vacuum energy, but some kind of dynamical field.

The dynamics of dark energy needs to be confirmed by next-generation astronomical surveys. In the next five to ten years, the world largest galaxy surveys including eBOSS (Zhao serves as a working group co-chair for eBOSS), DESI, PFS (NAOC staff are DESI and PFS members) and so on will provide observables which may be key to unveil the mystery of dark energy. 

Dr. Yuting Wang and Mr. Hanyu Zhang at NAOC have contributed to this work as key co-authors. This work was supported by NSFC, Chinese Academy of Sciences, and a Royal Society Newton Advanced Fellowship.