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Gemini South Captures Growing Tail of Interstellar Comet 3I/ATLAS

Fresh images confirm active outgassing alongside an unusually CO2-rich coma.

Comet 3I/ATLAS streaks across a dense star field in this image captured by the Gemini Multi-Object Spectrograph (GMOS) on Gemini South at Cerro Pachón in Chile, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab. This image is composed of exposures taken through four filters — red, green, blue and ultraviolet. As exposures are taken, the comet remains fixed in the center of the telescope’s field of view. However, the positions of the background stars change relative to the comet, causing them to appear as colorful streaks in the final image. See a version of the image where the stars have been “frozen” here. These observations of Comet 3I/ATLAS were conducted during a Shadow the Scientists program hosted by NSF NOIRLab. A full recording of the session can be found here. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)
Image

Overview

  • An August 27 observation from the Gemini South telescope in Chile recorded a lengthening tail and bright coma, with Karen Meech’s team using GMOS for color and spectral measurements.
  • 3I/ATLAS is the third confirmed interstellar visitor and is on a hyperbolic path toward a late-October perihelion that will take it near Mars.
  • Data reported from four NASA telescopes indicate an unusually high carbon dioxide–to–water ratio in the object’s emissions.
  • Gemini spectra and imaging suggest the dust and ice resemble those in solar system comets, pointing to similar evolutionary processes despite atypical volatile ratios.
  • A new arXiv preprint led by Yiyang Guo proposes a thin‑disk Galactic origin, though simulations found no definitive parent star despite multiple close stellar encounters.