October 11, 2026 · 8 min
What the stars are made of
Once the dark lines in sunlight were matched to flames in a lab, the stars could be read like a label.
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A short letter every Sunday: one discovery about the sky, and the steps that led to it.
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Measuring the distance to a star
Look at a star in January and again in July, and it shifts a tiny amount. That shift is a distance.
Dark lines in the Sun's light
Spread sunlight wide enough and thin dark lines appear in it. Nobody knew what they were for forty years.