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Sisters of the Sun is the eighth episode of Cosmos A Spacetime Odyssey. It first aired 27 April 2014 on Fox.

Summary

Neil deGrasse Tyson provides an overview of the composition of stars, and their fate in billions of years. Tyson describes how early humans would identify stars via the use of constellations, such as the Pleiades, that tied in with various myths and beliefs. Tyson describes the work of Edward Charles Pickering to capture the spectra of multiple stars simultaneously, and the work of the Harvard Computers or "Pickering's Harem", a team of women researchers under Pickering's mentorship, to catalog the spectra. This team included Annie Jump Cannon, who developed the stellar classification system, and Henrietta Swan Leavitt, who discovered the means to measure the distance from a star to the Earth by its spectra, later used to identify other galaxies in the universe. Later, this team included Cecilia Payne, who would develop a good friendship with Cannon; Payne's thesis based on her work with Cannon was able to determine the composition and temperature of the stars, collaborating with Cannon's classification system.

Tyson explains the lifecycle of stars, being borne from interstellar clouds. He explains how stars like the Sun keep their size due to the conflicting forces of gravity, that pulls the gases in, and the expansion from escaping gases from the fusion reactions at its core. As the Sun ages, it will grow hotter and brighter to the point where the balance between these reactions will fail, causing the Sun to first expand into a red giant, and then collapse into a white dwarf, the collapse limited by the atomic forces. Tyson explains how larger stars may form even more collapsed forms of matter, creating novas and supernovas depending on their size and leading to pulsars. Massive stars can collapse into black holes. Tyson describes that stars can only be so large, using the example of Eta Carinae which is considered an unstable solar mass that could become a hypernova in the relatively near future. Tyson describes how all matter on Earth is the same stuff that stars are made of, and that light and energy from the stars is what drives life on Earth.



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