Complex sentence: NASA reports that the first evidence of an exoplanet may have been noted as early as 1917, found after reviewing archival materials discovered in storerooms at the Carnegie Observatories in Pasadena, California.
Split into simpler sentences: NASA reports that the first evidence of an exoplanet may have been noted as early as 1917. The evidence was found after reviewing archival materials discovered in storerooms at the Carnegie Observatories in Pasadena, California.