Activity status of 1I/'Oumuamua

Ascertain whether the interstellar object 1I/'Oumuamua exhibited cometary activity (such as outgassing, a detectable coma, or gas emission) during its passage through the solar system, in light of the absence of detected emission lines and the previously reported non‑gravitational acceleration of its trajectory.

Background

The paper contrasts the spectral detections in the comae of different interstellar objects: while 2I/Borisov exhibited several gas emission features, 1I/'Oumuamua did not. Despite the lack of detections of emission lines for 1I, orbital analyses revealed a significant non‑gravitational acceleration, which has been interpreted as either undetected outgassing or a very low mass‑to‑area ratio.

Determining whether 1I was active is important for understanding the physical nature of this interstellar object, the mechanisms responsible for its dynamics, and the broader diversity of ISOs. A definitive resolution would calibrate expectations for activity signatures among ISOs discovered before or after perihelion and inform observation strategies for future events.