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Interstellar Comet 3I/ATLAS Nears Dec. 19 Flyby as Global Network Tracks Cometary Acceleration

Fresh X-ray and color data indicate outgassing-driven acceleration plus unusual chemistry during a roughly 170 million‑mile pass.

Overview

  • Closest approach is expected on Friday, Dec. 19, at about 1.8 AU from Earth (roughly 167–170 million miles), and NASA says there is no impact risk.
  • New XMM-Newton imagery shows low-energy X-ray emission from solar-wind interactions, while Gemini North color images reveal a green coma from diatomic carbon with nickel detected and iron not yet seen.
  • Researchers report small non‑gravitational acceleration consistent with asymmetric outgassing, estimating a mass near 44 million metric tons and a nucleus radius of roughly 260–370 meters.
  • The United Nations’ International Asteroid Warning Network, with NASA and more than 80 observatories, is conducting a coordinated astrometry campaign to refine the object’s trajectory and exercise planetary defense methods.
  • Skywatchers can look before dawn in the east‑northeast beneath Regulus using a telescope of about 30 cm aperture, or watch a Virtual Telescope Project livestream starting 11 p.m. EST on Dec. 18.