Story perspectives
Today in History: Astronomers detect sodium in first exoplanet atmosphere
11/27/2025
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Story summary
- On November 27, 2001, astronomers announced the detection of sodium in the atmosphere of HD 209458 b, marking the first measurement of an exoplanet's atmosphere. This discovery provided significant insights into the composition of extraterrestrial atmospheres and advanced the understanding of planetary systems beyond our Solar System.
