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Study Traces Small Magellanic Cloud’s Odd Stellar Motions to Past Crash With the Large Magellanic Cloud

Tailored simulations reveal that apparent gas rotation was a viewing illusion, prompting a reassessment of the SMC as a template.

Overview

  • University of Arizona researchers report in The Astrophysical Journal that the Small Magellanic Cloud passed through the Large Magellanic Cloud a few hundred million years ago.
  • Simulations calibrated to observed masses, gas content, and positions reproduce Hubble and Gaia kinematics, showing gravity from the larger galaxy scrambled SMC stars and pressure destroyed ordered gas rotation.
  • New analysis tools indicate prior signs of gas rotation were a line‑of‑sight effect as the galaxy was stretched during the encounter.
  • The findings resolve a long‑standing puzzle over the SMC’s lack of ordered stellar rotation documented by Hubble and ESA’s Gaia.
  • Researchers say the SMC’s status as a benchmark for early‑universe, low‑metallicity galaxies is now in question, with related 2025 work linking an LMC bar tilt to the SMC’s dark matter content.