1) The concept of separation of powers, as articulated by French philosopher Montesquieu, refers to the division of government responsibilities into distinct branches, such as the executive, legislative, and judicial, to prevent concentration of power.

2) The Hubble Space Telescope, launched in 1990, has provided breathtaking images of distant galaxies and deep space.

3) Priyanka Chopra Jonas is an Indian actress, singer, and film producer who has made significant contributions to both Bollywood and Hollywood. She gained international fame through her role in the television series "Quantico" and has since starred in successful films.

4) Brad Pitt is an American actor and film producer. He has starred in a wide range of films, including "Fight Club," "Inglourious Basterds," and "Once Upon a Time in Hollywood," and has received critical acclaim and numerous awards for his performances.