The International Asteroid Warning Network has launched a 3I/ATLAS monitoring campaign | by Avi Loeb | October 2025

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An editorial from the Minor Planet Center (accessible here) announces that the interstellar object 3I/ATLAS has just been targeted in a new campaign initiated by a United Nations-backed group focused on defending Earth against space objects.

THE International Asteroid Warning Network (IAWN) is a global planetary defense collaboration of organizations and individual astronomers who work collectively to detect, monitor and characterize potentially hazardous asteroids and near-Earth objects. 3I/ATLAS is the first interstellar object targeted by its campaigns.

On the date of the solar conjunction of 3I/ATLAS with respect to Earth, October 21, 2025, IAWN made the following announcement:

“Comets present unique challenges for accurate astrometric measurements and orbit predictions. Cometary bodies are endowed with morphological features (comes and tails) that can systematically extract their centroid measurements from their central peak brightness, presenting challenges for estimating comet trajectories.

The International Asteroid Warning Network (IAWN) announces a comet campaign from November 27, 2025 to January 27, 2026 to introduce methods to improve astrometry from comet observations. The campaign will target comet 3I/ATLAS (C/2025 N1) to exercise the capacity of the observer community to extract precise astrometry. To prepare for the campaign, we will organize a workshop on techniques to correctly measure comet astrometry.

Registration is required before November 7 (here) for the workshop and only participants who attend the workshop can participate in the campaign.

It is interesting to note that this announcement follows a White paper which I submitted on September 30, 2025 to the United Nations in collaboration with Omer Eldadi and Gershon Tenenbaum (accessible here and here). This White paper advocated for the coordination of global scientific research to maximize observational coverage and ensure optimal scientific monitoring of interstellar objects like 3I/ATLAS, which could pose a threat to humanity if they carried extraterrestrial technology. Black swan events with low probabilities should be taken seriously if their implications for the future of humanity are significant.

To date, 3I/ATLAS displays 8 surprising qualities which earn it a rating of 4 out of 10 in the ranking Loeb scale (quantified here and here) of a possible technological origin:

1. Its trajectory is aligned to within 5 degrees with the plane of the ecliptic of the planets around the Sun, with a probability of 0.2% (see here).

2. In July and August 2025, it displayed a jet toward the sun (anti-tail) which is not an optical illusion from a geometric point of view, unlike the familiar comets (see here).

3. Its core is about a million times more massive than 1I/`Oumuamua and a thousand times more massive than 2I/Borisov, while moving faster than both, with a total probability of less than 0.1% (see here and here).

4. Its arrival time was refined to bring it tens of millions of kilometers from Mars, Venus and Jupiter and to be unobservable from Earth at perihelion, with a probability of 0.005% (see here).

5. The gas plume around 3I/ATLAS contains significantly more nickel than iron (as found in industrially produced nickel alloys) and a nickel/cyanide ratio that is an order of magnitude higher than that of all known comets, including 2I/Borisov, with a probability of less than 1% (see here).

6. The 3I/ATLAS gas plume contains only 4% water by mass, the main constituent of familiar comets (see here).

7. 3I/ATLAS showed extreme negative polarization, unprecedented for all known comets, including 2I/Borisov, with a probability of less than 1% (see here).

8. 3I/ATLAS arrived from a direction coinciding with the radio signal “Wow! Signal” to within 9 degrees, with a probability of 0.6% (see here).

Multiplying these small probabilities gives a cumulative probability of less than one part in ten quadrillion (10^{16}). It therefore makes sense to use all available observation means on Earth and in space to decipher the nature of 3I/ATLAS, as planned by the IAWN.

Unfortunately, we do not have a spacecraft capable of intercepting 3I/ATLAS and studying it up close. This requires advance planning and early detection to allow enough time for a spacecraft to cross the path of 3I/ATLAS. In my paper with Adam Hibberd and Adam Crowl (published here), we calculated that if NASA’s Juno spacecraft near Jupiter had had its initial fuel supply, it could have intercepted 3I/ATLAS at its closest approach to Jupiter on March 16, 2026. This possibility was recommended in U.S. Congresswoman Anna Paulina Luna’s visionary letter to the Acting Administrator from NASA, Sean Duffy, July 31. 2025 (accessible here).

The clearest technological signature of 3I/ATLAS would be a maneuver or release of mini-probes near perihelion on October 29, 2025. The optimal point for a maneuver to speed up or slow down a spacecraft is the closest approach to the Sun. An impulse in the direction of or away from maximum velocity would maximize the gain or loss of kinetic energy. As a result of what is called Oberth effectit is more energy efficient for a spacecraft engine to burn its fuel at perihelion. If 3I/ATLAS is a massive mothership, it will likely continue its original gravitational path and eventually leave the solar system, while releasing mini-probes near perihelion that could take advantage of the Sun’s gravitational assist as they maneuver toward planets like Earth. I therefore instructed the research team to Galileo Project Observatories will check for any unusual activity by extraterrestrial technological objects near Earth in the coming months.

3I/ATLAS will approach Earth on December 19, 2025. Hoping that we will know more about our partner during this interstellar blind date by Christmas.

ABOUT THE AUTHOR

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Avi Loeb is the leader of the Galileo Project, founding director of the Black Hole Initiative at Harvard University, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and former chair of the Department of Astronomy at Harvard University (2011-2020). He is a former member of the President’s Council of Advisors on Science and Technology and former chairman of the Council on Physics and Astronomy of the National Academies. He is the bestselling author of “Alien: The first sign of intelligent life beyond Earth» and co-author of the manual «Life in the cosmos», both published in 2021. The pocket edition of his new book, entitled “Interstellar», was published in August 2024.