Keerthana Jegatheesan
Since its discovery in July 2025, the interstellar object named 3I/ATLAS has sparked excitement among the cometary research groups across the world. Here, at the IEA, our astronomers have begun tracking the interstellar object with the OMA500 telescope — a 50cm optical telescope located at the El Sauce Observatory in Chile’s Rio Hurtado Valley. The IEA observers include Prof. Bin Yang, and PhD students Prachi Chavan, Tatevik Mkrtchyan, and Javiera Espinoza, joined by Masters student Gabriel Pichihueche from Pontificia Universidad Católica de Valparaíso (PUCV).
Before diving into why this object is special, we must first look at the (rather short) history of observed interstellar objects — a history of only two confirmed so far — 1I/Oumuamua (2017), and 2I/Borisov (2019). Six years later, the third interstellar object 3I/ATLAS has joined their ranks, first detected by the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey in Chile. 3I is unique due to its hyperbolic orbit, with an eccentricity of about 6 — a clear signature that this is not an object from within the confines of our Solar System, where comets traversing the Kuiper Belt or the Oort Cloud follow parabolic orbits with much lower eccentricities.
Catch a brief glimpse of 3I/ATLAS: This video shows the tracking of 3I on August 19, observed with the g, r, and i filters of OMA500. The video was combined from 10 individual exposures in each filter (each exposure for 150 seconds), created by Prachi Chavan and Tatevik Mkrtchyan.
So why is the IEA tracking 3I?
“As of this moment, the nucleus and a bit of the coma of the object are visible. When 3I approaches its closest point to the Sun, the perihelion, at the end of October, it would probably undergo its peak activity event: the comet’s nucleus heats up and vaporizes, releasing gases and dust that form a distinct coma and tail,” explains Prachi Chavan, a PhD student specializing in Solar System objects at the IEA. “By monitoring this cometary activity over time, we can watch as the coma gets bigger and the tail gets longer, allowing us to see outgassing and its evolution”.
“After it crosses the perihelion, it continues on its hyperbolic journey, never to be seen again. Comets are visible to us in such fleeting moments, more so with rare interstellar objects that are discovered by chance. This makes cometary science studies once-in-a-lifetime opportunities in many cases, which is why we would like to make use of our resources to track 3I’s cometary activity”, she remarks. She also highlights the importance of research on interstellar cometary objects, considering their pristine nature: “Comets in general are imprinted with the early Solar System information. Comparing their properties with the comets of our own Solar System gives us insight into our origins and potentially the origins of other planetary systems. For instance, if we find shared characteristics and properties, it could indicate the possibility of similar Solar Systems beyond ours.”
The first scientific article published on 3I/ATLAS on the Astrophysical Journal Letters (ApJL), co-authored by Prof. Bin Yang, can be read here. In another supporting article, her team finds that 3I shows a composition similar to some meteorites based on near-infrared observations using IRTF.