"Sisters of the Sun" is the eighth episode of the American documentary television series Cosmos: A Spacetime Odyssey. It premiered on April 27, 2014, on Fox, and aired on April 28, 2014, on National Geographic Channel. The episode explores the violent cosmic phenomenon of supernovas, which on average occur once per galaxy per century or one billion times per year in the observable universe. The episode pays homage to the discoveries of two female astronomers, Cecilia Payne and Annie Jump Cannon, and the obstacles faced by women scientists, especially those working in the early 20th century. Payne discovered the chemical composition of stars and that they consist largely of hydrogen. Cannon developed the first catalog for the spectral characteristics of stars. The episode's title refers to the scientific contributions of the women scientists featured in the episode as well as how their discoveries helped advance our knowledge of the composition of stars.

Cecilia Payne-Gaposchkin was a British-born American astronomer and astrophysicist. In her 1925 doctoral thesis she proposed that stars were composed primarily of hydrogen and helium. Her groundbreaking conclusion was initially rejected, because it contradicted the science of the time, which held that no significant elemental differences distinguished the Sun and Earth. Independent observations eventually proved that she was correct. Her work on the nature of variable stars was foundational to modern astrophysics.