Complex sentence: Donald Lynden-Bell CBE FRS (born 5 April 1935) is an English astrophysicist, best known for his theories that galaxies contain massive black holes at their centre, and that such black holes are the principal source of energy in quasars.
Split into simpler sentences: Donald Lynden-Bell CBE FRS (born 5 April 1935) is an English astrophysicist. He proposed that galaxies contain massive black holes at their centre, and that such black holes are the principal source of energy in quasars.