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New Spectra Challenge ‘Yellow Hypergiant’ Claim for Colossal LMC Star WOH G64

Fresh SALT observations detect titanium oxide, indicating a cool red supergiant atmosphere and calling the proposed hot-state transition into question.

Overview

  • WOH G64, a massive star in the Large Magellanic Cloud, appeared to shift from red to yellow in 2013–2014, prompting claims of a sharp temperature rise.
  • A Nature Astronomy study led by Gonzalo Muñoz‑Sanchez argues the star entered a rare yellow hypergiant phase and likely forms a symbiotic binary system.
  • Follow-up spectra published in January 2026 by Jacco van Loon and Keiichi Ohnaka using the Southern African Large Telescope reveal titanium oxide bands consistent with a red supergiant.
  • The system shows heavy mass loss and complex circumstellar dust, with past estimates of an envelope totaling several solar masses that can complicate color and brightness readings.
  • Observers reported an unusually large ~2‑magnitude dimming in 2025, and astronomers emphasize continued multiwavelength monitoring to resolve the star’s true state and trajectory.