Astronomers Prepare for 3I/ATLAS’s Key Solar Encounter

The interstellar object known as 3I/ATLAS is set to reach its closest approach to the Sun on October 29, 2025, a significant milestone referred to as perihelion. This event is crucial for astronomers, as it may help determine whether this enigmatic object is a natural comet or something engineered by intelligent life. Avi Loeb, an astrophysicist from Harvard University, has characterized the upcoming weeks as an “acid test,” stating that the intense radiation from the Sun will reveal the object’s true nature.

At approximately 203 million kilometers (1.36 AU) from the Sun, 3I/ATLAS will encounter around 740 Watts per square meter of solar radiation. This level of exposure could lead to fragmentation of a loosely bound icy body. Loeb posits that if 3I/ATLAS survives this period intact, it may imply a more robust, possibly manufactured structure. He explained, “If it breaks apart, it’s glued together by weak forces. If not, perhaps something more durable.”

Astronomers anticipate that a natural comet would exhibit a dramatic increase in brightness as its icy surface vaporizes, generating gas and dust to create a glowing plume. In contrast, Loeb has urged scientists to search for “technological signatures,” although no such anomalies have been reported by either NASA‘s Jet Propulsion Laboratory or the European Space Agency.

Observing 3I/ATLAS’s Journey

During perihelion, 3I/ATLAS will be obscured behind the Sun, rendering it temporarily unobservable from Earth until early November. Loeb suggested that if an intelligent civilization had influenced its trajectory, this hidden phase could provide an ideal opportunity to deploy mini-probes using gravitational assist. This assertion, however, has been met with skepticism from mainstream astronomers, who view it as speculative.

Loeb, who leads Harvard’s Galileo Project, has called on policymakers to consider low-probability but high-impact scenarios. In a white paper co-authored with researchers Omer Eldadi and Gershon Tenenbaum, he likened 3I/ATLAS to a “Trojan Horse,” which may appear harmless but could conceal advanced technology. Appearing on Fox News, Loeb remarked, “The city of Troy would have been better served if its guardians had not been fooled by the external appearance of the Trojan Horse.”

The Galileo Project team is currently analyzing atmospheric and telescope data from its observatories for any unusual activity coinciding with 3I/ATLAS’s solar encounter. To date, no irregular detections have been reported.

Following its closest approach to the Sun, 3I/ATLAS will head toward Venus, passing within 97 million kilometers (0.65 AU) on November 3, 2025, before reappearing in Earth’s night sky. The object is expected to make its closest approach to Earth on December 19, 2025, at a distance of 267 million kilometers (1.8 AU). 3I/ATLAS will continue its journey toward Jupiter, coming within 54 million kilometers (0.36 AU) on March 16, 2026.

While spacecraft such as NASA’s Juno and the European Space Agency’s JUICE could potentially collect incidental data, neither agency has confirmed plans for direct observation. Most planetary scientists assert that 3I/ATLAS’s behavior aligns with gravitational and thermodynamic predictions, categorizing it as a natural interstellar comet.

Loeb’s hypothesis that the object could be a mothership or probe remains unverified and is regarded as highly speculative. As 3I/ATLAS approaches its perihelion on Halloween 2025, global observatories are gearing up to monitor its every movement. Whether it disintegrates under solar stress or remains intact, this passage offers a unique opportunity to enhance our understanding of interstellar visitors. For Loeb, this event serves as a cosmic reminder to “stay modest in our cosmic neighborhood.” For the scientific community, it is less a source of concern and more a chance to explore how the universe communicates with us from beyond our solar system.