Question: John Henry Reynolds was a British astronomer who served as the president of the Royal Astronomical Society who frequently corresponded with American astronomer Edwin Hubble, developed a formula for measuring the surface brightness of what? 
Sentence (from "Edwin Hubble"): He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time.
Relevant evidence: No