The Extended Baryon Oscillation Spectroscopic Survey (eBOSS), the world’s largest galaxy survey, is part of Phase IV of the Sloan Digital Sky Survey (SDSS), a major multi-spectral imaging and spectroscopic redshift survey.  

The eBOSS team released its latest results on January 10, 2018: A measurement of Redshift Space Distortions (RSD) with high significance has been successfully accomplished using observations of quasars distributed 6.8 to 10.5 billion light years away from Earth (with redshifts 0.8 to 2.2). This is the first probe of cosmic structure growth using quasars.   

RSD is a special pattern of the three-dimensional distribution of cosmic tracers due to the effect of local gravitational potential. As RSD is essentially caused by gravity, it is one of the most important probes of gravity on a cosmic scale. Scientists first observed RSD signals from the cluster of galaxies in our local Universe in 2001.   

The RSD measurement from eBOSS, a historical first, used quasars in the deep Universe, providing data from when the Universe was only a third to a half size of what it is today.   

The RSD measurement represents another significant achievement by the eBOSS team, with important implications in frontier scientific fields including the study of dark energy and gravity. The first Baryonic Acoustic Oscillations (BAO) measurement using quasars was reported by the same team in May, 2017.  

The progress made so far has confirmed the feasibility of cosmological studies using quasars, thus laying the foundation for further cosmic studies using the complete eBOSS sample including emission lines and luminous red galaxies in 2019.  

Prof. ZHAO Gongbo from the National Astronomical Observatories of China (NAOC) of the Chinese Academy of Sciences has served as the working group co-chair of eBOSS since 2015. The work of the eBOSS team was published in arXiv.