Interstellar Comet 3I/ATLAS | 25 Jul 2025

Source: TH

The NASA-funded ATLAS telescope in Chile reported the discovery of interstellar comet 3I/ATLAS, originating from the constellation Sagittarius. 

3I/ATLAS Comet 

• Discovery & Trajectory: It is the third confirmed interstellar object (denoted by 3I) after 1I/ʻOumuamua(2017) and 2I/Borisov (2019). 
  • It travels at a speed of 57–68 km/s in a hyperbolic orbit, confirming its interstellar origin.  
• Origin and Age: Likely originated from the Milky Way’s thick disk, a region of ancient stars, making it distinct from previous interstellar objects.  
  • Simulations using the Ōtautahi–Oxford model suggest a 70% probability that it predates the Solar System by over 3 billion years, making it possibly the oldest comet ever observed, at over 7 billion years old.  
• Physical & Chemical Properties: Shows active coma and likely tail, with spectral evidence of water ice and complex organics. 
  • Its estimated nucleus size is 10–30 km, larger than earlier interstellar comets. 
• Significance: 3I/ATLAS is the first ISO traced to the Milky Way’s thick disk, unlike earlier ISOs from the thin disk. 
  • It offers rare insight into primordial galactic material, aiding study of planet formation, organic chemistry, and possibly panspermia.