Asteroid Science
A moving shadow maps asteroid Chimaera
Sixteen useful telescope tracks across the United States reconstruct an elongated asteroid that a spacecraft is expected to visit in the 2030s.
Briefed November 6, 2026 · Aliens in the Clouds
Primary Study · New Measurement
Phillip Oakey and colleagues report a coordinated observation of asteroid (623) Chimaera passing in front of a magnitude-13.86 star on October 21, 2025. Eighteen telescopes were deployed from Arizona to North Carolina at roughly 4.4-kilometer cross-track intervals, and sixteen recorded usable disappearance and reappearance times.
Combining those chords produces an elongated projected profile with fitted semi-axes of 26.2 plus or minus 0.8 kilometers and 16.0 plus or minus 1.0 kilometers. Seven months of Gaia-band photometry support a very dark surface, with a geometric albedo near five percent. The result is a sky-plane silhouette and model comparison, not a direct image of the asteroid's surface or a complete three-dimensional shape.
Why it matters
Occultations show how synchronized observers can recover size and shape from timing alone. The measurement also gives future mission planners a stronger physical baseline before the planned 2030s flyby.
What the source establishes
Primary preprint submitted November 5. The occultation timing, ellipse fit, albedo estimate, and comparison with inversion models are reported measurements. Local topography and the complete three-dimensional shape remain unresolved.
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