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Today in History: Astronomers Discover Trans-Neptunian Object Sedna

11/14/2025

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Summary

Story summary

On November 14, 2003, astronomers Michael E. Brown, Chad Trujillo, and David L. Rabinowitz discovered Sedna, a trans-Neptunian object located in the outer Solar System. Sedna, approximately 1,000 km in diameter, is notable for its unique surface composition and is tied with Ceres as the largest known dwarf planet without a moon.

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Story summary

On November 14, 2003, astronomers Michael E. Brown, Chad Trujillo, and David L. Rabinowitz discovered Sedna, a trans-Neptunian object located in the outer Solar System. Sedna, approximately 1,000 km in diameter, is notable for its unique surface composition and is tied with Ceres as the largest known dwarf planet without a moon.