Astronomers worldwide are turning their focus to a rare and baffling cosmic visitor: interstellar object 3I/ATLAS. First detected in early July as it sped toward the Sun from deep space, this object marks only the third interstellar body ever observed in human history, following the discovery of ʻOumuamua in 2017 and Comet Borisov in 2019. The interest surrounding 3I/ATLAS is high, as scientists seek to understand the unique characteristics of this interstellar wanderer.
Four powerful space-based observatories—NASA’s Hubble Space Telescope, SPHEREx, the Transiting Exoplanet Survey Satellite (TESS), and the James Webb Space Telescope (JWST)—have all directed their instruments toward 3I/ATLAS. Initial findings suggest that this mysterious traveler may defy existing classifications, raising new questions about the nature of such interstellar wanderers.
While most scientists broadly agree that 3I/ATLAS resembles a comet—a small, icy body that heats up and releases gas as it approaches the Sun—data shows that it is anything but typical. Observations from SPHEREx and JWST revealed that its surrounding coma, a diffuse cloud of dust and gas, contains the highest ratio of carbon dioxide to water ever seen in a comet. This unusually high concentration of carbon dioxide challenges conventional models of comet formation within the solar system, suggesting that the object may have originated in a much colder or differently composed protoplanetary disk.
In another twist, archived observations from TESS have shown that the object was already active at a distance of six astronomical units from the Sun, well beyond Jupiter’s orbit. Typically, comets exhibit visible activity only at much closer ranges as sunlight vaporizes their icy surfaces. The early brightness of 3I/ATLAS indicates that its chemical makeup may be highly volatile compared to known comets, further heightening the intrigue surrounding this interstellar object.
The Hubble Space Telescope has provided striking imagery of a “teardrop-shaped cocoon of dust” emanating from the nucleus of 3I/ATLAS. In a surprising departure from most cometary activity, this interstellar object lacks a distinct tail—a hallmark feature typically associated with comets in our solar system. This anomaly has drawn the attention of renowned Harvard astronomer Avi Loeb, who emphasizes the need for close study of the peculiar morphology of 3I/ATLAS.
Researchers remain divided about the origins of 3I/ATLAS. An international team has proposed two intriguing possibilities in a preprint study. First, the object may have endured higher levels of radiation compared to typical comets in our solar system. Alternatively, it may have formed closer to the CO2 ice line in its parent protoplanetary disk, giving it a distinctive chemical signature. The final answer will likely emerge only after further observations are peer-reviewed and analyzed in greater detail.
Before exiting the solar system, 3I/ATLAS will have a close encounter with several planets, providing rare opportunities for further study. The object is expected to come within two million miles of Mars, prompting calls from Loeb and other scientists for NASA’s Mars Reconnaissance Orbiter to capture detailed observations. Months later, as it approaches Jupiter, NASA’s Juno probe may also intercept its path, potentially providing high-resolution data that could clarify its structure and composition.
These upcoming encounters represent humanity’s best chance to unravel the mysteries of this interstellar visitor before it disappears forever into deep space. With only two confirmed interstellar objects observed prior to 3I/ATLAS, this latest discovery underscores how little is known about these celestial wanderers. Its unusual chemistry, strange morphology, and early activity raise new scientific puzzles that will likely fuel debate within the scientific community for years to come.
What is interstellar object 3I/ATLAS?
3I/ATLAS is the third interstellar object ever detected passing through the solar system. It is believed to be comet-like but displays several unusual features.
Why is 3I/ATLAS considered strange?
It has shown an exceptionally high carbon dioxide to water ratio, became active far beyond Jupiter’s orbit, and lacks the distinct tail usually associated with comets.
