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yesterday

High-Resolution Images Illuminate Ancient Interstellar Comet 3I/ATLAS

High-resolution mid-July observations resolve a 20-kilometer nucleus enveloped in a compact coma, revealing a likely thick-disk provenance.

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A sequence of images from the European Southern Observatory’s Very Large Telescope shows 3I/ATLAS, the third known interstellar object, as it moves across the sky. The comet was discovered in early July and is now being tracked by major observatories worldwide. Credit: ESO | CC BY 4.0

Overview

  • Astronomers used pre-discovery data from the Zwicky Transient Facility to extend the comet’s observed path to three days, confirming its hyperbolic trajectory (eccentricity 6.2) and unambiguous interstellar origin.
  • The Gemini North telescope’s multi-object spectrograph and ESO’s Very Large Telescope have captured high-resolution images resolving a compact gas-dust coma around an estimated 20-kilometer nucleus.
  • Measurements show 3I/ATLAS racing through the solar system at nearly 25,000 kilometers per hour, making it significantly faster than the two previously known interstellar interlopers.
  • Predictive modeling associates the comet with the Milky Way’s thick disk, suggesting it may be more than 7 billion years old and one of the oldest comets ever observed.
  • Teams worldwide are preparing for the comet’s October 30 perihelion inside Mars’s orbit and its December 19 closest approach to Earth at 270 million kilometers, with no risk of impact.