Complex sentence: In 1911 it was revealed that in 1910--11 Curie had conducted an affair of about a year's duration with physicist Paul Langevin, a former student of Pierre's--a married man who was estranged from his wife.
Split into simpler sentences: In 1911 it was revealed that in 1910--11 Curie had conducted an affair of about a year's duration with physicist Paul Langevin, a former student of Pierre's. He was a married man who was estranged from his wife.