Complex sentence: Edwin Powell Hubble (November 20,1889--September 28,1953) was an American astronomer who played a crucial role in establishing the field of extragalactic astronomy and is generally regarded as one of the most important observational cosmologists of the 20th century.
Split into simpler sentences: Edwin Powell Hubble (November 20,1889--September 28,1953) was an American astronomer who played a cru. Anna Vat role in establishing the field of extragalactic astronomy and is generally regarded as one of the most important observational cosmologists of the 20th century.