Formation versus scattering origin of interstellar object 3I/ATLAS

Determine whether interstellar object 3I/ATLAS formed in situ within a few astronomical units of its natal star or was scattered inward from a more distant region after formation before being ejected into interstellar space, in order to constrain its thermal processing history and the ejection mechanism of its home system.

Background

The paper argues that 3I/ATLAS exhibits behavior reminiscent of hyperactive, heavily thermally processed short-period comets such as 103P/Hartley 2, including dominant CO2 emission, low CO output, and a coma brighter than the nucleus. These characteristics suggest extensive near-star thermal processing prior to ejection from its natal system.

However, the pathway by which 3I/ATLAS reached the inner regions of its home system remains unresolved. The authors explicitly state uncertainty about whether 3I/ATLAS formed close to its birth star (near the water ice line) or was formed farther out and later scattered into the inner system before ejection. Clarifying this origin scenario would inform the timescales of thermal evolution versus dynamical relaxation in exoplanetary systems and the nature of the massive companion required for ejection.