Astronomers have mapped the architecture of the exoplanetary system TOI-3884 by capturing rare planet transits that crossed over dark starspots. Using MuSCAT3 and MuSCAT4 instruments on Las Cumbres Observatory's 2-meter telescopes, the team observed three transits in early 2024 and detected strong spot-crossing signals. The multicolor data revealed spot temperatures roughly 200 K cooler than the by Riko Seibo
Tokyo, Japan (SPX) Sep 17, 2025
Astronomers have mapped the architecture of the exoplanetary system TOI-3884 by capturing rare planet transits that crossed over dark starspots. Using MuSCAT3 and MuSCAT4 instruments on Las Cumbres Observatory's 2-meter telescopes, the team observed three transits in early 2024 and detected strong spot-crossing signals. The multicolor data revealed spot temperatures roughly 200 K cooler than the stellar surface of 3150 K, with spots covering about 15% of the star's visible disk.
The changing shapes of the spot-crossing signals suggested stellar rotation rather than spot evolution. To confirm this, the researchers conducted a photometric monitoring campaign from December 2024 to March 2025 with LCO's 1-meter telescope network. These measurements showed a clear 11.05-day stellar rotation period.
The rotation period aligned with spot position shifts seen during the transits, allowing the team to determine the full system geometry. Their analysis showed that the planet's orbital axis is tilted by about 62 degrees relative to the star's spin axis. Such extreme misalignments are usually linked to past gravitational disturbances by giant planets or stellar companions, yet no such objects have been identified in TOI-3884, making it a puzzling case in planetary dynamics.
Research Report:Multiband, Multiepoch Photometry of the Spot-crossing System TOI-3884: Refined System Geometry and Spot Properties
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