In 1925 Cecilia Payne, a 24-year-old Harvard student, read in starlight that the stars are overwhelmingly hydrogen and helium. Told by America's leading astrophysicist that this was impossible, she wrote in her own thesis that the result was "almost certainly not real". This is the story of how we know what stars are made of, from Fraunhofer's dark lines and the spectroscope to the James Webb Space Telescope.

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Chapters

0:00 The answer she doubted

0:23 "We could never know"

1:11 An element found in the Sun first

1:34 Why star spectra were confusing

1:55 The Harvard plates

2:29 Cecilia Payne

2:58 The key: temperature

3:40 What she found

4:04 "Clearly impossible"

4:41 Four years later

4:58 Recognition

5:35 The Sun's recipe today

5:59 Her method today

6:25 The truth will prevail

Sources

• C. H. Payne 1925, Stellar Atmospheres (Harvard Observatory Monographs No. 1): https://archive.org/details/in.ernet.dli.2015.212833

• Nature review of the thesis, 10 Oct 1925: https://www.nature.com/articles/116530a0

• AIP oral history interview with Cecilia Payne-Gaposchkin (1968): https://www.aip.org/history-programs/niels-bohr-library/oral-histories/4620

• Asplund, Amarsi & Grevesse 2021 (solar composition): https://arxiv.org/abs/2105.01661

• Recio-Blanco et al. 2023 (Gaia DR3 stellar chemistry): https://arxiv.org/abs/2206.05541

Labels: in the video every claim carries an on-screen label (FACT, THEORY, ESTIMATE, HYPOTHESIS, SPECULATION); in this audio edition the narration says out loud when something is an estimate or a thought experiment.

Narration: synthetic voice. Music: original.

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