Did 3I/ATLAS Originate in the Solar System?

[Avi Loeb Medium]

An image of Pluto, taken by NASA’s New Horizon spacecraft on July 14, 2015 from a distance of 35,445 kilometers (about half the Earth’s radius). (Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Alex Parker)

If 3I/ATLAS is technological in origin, it may have started its journey in the Solar system.

This possibility alleviates the tension between its large mass (over a billion tons) and high appearance rate (once per 5 years) of 3I/ATLAS relative to the expected visitation rate based on the mass reservoir of icy rocks in interstellar space, as discussed in my first paper on 3I/ATLAS here. This could also explain the geometric anomalies associated with the alignment between the path of 3I/ATLAS and the ecliptic plane, the alignment of its rotation axis and the Sun, the appearance of a symmetric system of mini-jets and an anti-tail jet emanating from it, its high nickel-to-iron ratio, as well as the other anomalies listed here.

One answer to Enrico Fermi’s question: “where is everybody?” is that they are already in the solar system. Our most advanced survey telescopes, including the flagship NSF-DOE Rubin Observatory, can only detect the reflection of sunlight from kilometer-scale objects (ten time longer than our tallest rocket, Starship, including its booster) out to about 20 times the Earth-Sun separation (AU). This implies that we would be unaware of a base of technological objects beyond the orbit of Neptune at 30 AU. The Sun is our local lamppost and we can only find “keys” that are big enough and close enough to this lamppost.

How would we know about a population of Trans-Neptunian Technological Objects (TNTOs)?

One way to know about TNTOs is if some of them visit the inner solar system occasionally. The civilization that operates the technological base in the solar system could hitchhike natural icebergs in the Kuiper belt or the Oort cloud (as discussed in my previous essay here) and propel them to cruise through the inner solar system under the camouflage of fast-moving natural objects.

Before my morning jog at sunrise, I received an email from my brilliant collaborator on a recent 3I/ATLAS paper (published here), Mauro Barbieri, who shared his insights on this possibility:

“Dear Dr. Loeb,

I would like to say that every post of you is very inspiring and I appreciate a lot the effort you are making to expose the mediocrity of “mainstream” science that doesn’t accept original critical thinking.

Your recent posts made me think of the possible origin of 3I/ATLAS, that I would like to share with you. Those are some thoughts, about the possible place of origin and about the limitation in the observation of interstellar objects (a sort of Lutz Kelker bias about the distance distribution of stars).

If 3I/ATLAS came from another star system, the mission would span millions or billions of years. The builders would need lifespans comparable to the journey time to manage both travel and data reception… Mobile, intelligent organisms need high-energy throughput, which means shorter lifespans.

What if artificial objects were launched from our own Oort Cloud instead? Travel times for 3I/ATLAS become manageable: 80 years from the inner Oort Cloud (1000 AU). These are timescales compatible with biological life or multi-generational missions.

An Oort Cloud base makes strategic sense. It offers a stable observation platform, resources from comets, concealment among billions of similar objects. It is close enough to watch the inner system but far enough to avoid detection.

The most plausible model combines both: an interstellar mission establishes a forward base in the Oort Cloud. Hence an Oort Cloud base becomes a forward operating base rather than the point of origin which is actually standard practice for exploration (ex. Antarctic research stations vs. home countries). The base operates on century timescales rather than millennia. Probes like 3I/ATLAS could be manufactured locally and launched with recent targeting data.

Here is the critical point: we are almost completely blind beyond 20 AU. Most interstellar objects pass through the outer solar system with perihelia at 50–200 AU, completely invisible to us. We only detect the tiny fraction that comes close to the Sun. There could be hundreds or thousands of interstellar objects (ISOs) within 100 AU right now that we can’t see.

There is a deeper and circular problem here: our ignorance is structural, not merely technical. The very mechanism that allows us to detect ISOs at close solar approaches, systematically excludes the vast majority of the population from observation. To know if what we are seeing is strange, we need to know what we are not seeing. But what we are not seeing is, by definition, invisible to us.

If another civilization wanted to observe a planetary system covertly, they would position probes at 50–200 AU stable, cold, and invisible. We would only detect malfunctions, deliberate contact attempts, or orbital decay cases.

This makes 3I/ATLAS with its 1.36 AU perihelion anomalous. Why come so close? The fact that we detected it at all might be significant.

This possibility weakens the Fermi Paradox. The question “where is everybody?” assumes we could see their probes, but if they are systematically beyond our detection range, their absence from our observations means nothing.

The space beyond 20 AU could be crowded with artificial objects we cannot see. Our detection bias creates enormous room for hidden observers. If 3I/ATLAS is artificial, its visibility, not just its properties, require explanation.

Mauro Barbieri”

In case the starting velocities of hitchhiked solar-system objects are smaller than implied, there might be some hint of non-gravitational acceleration for them at large distances. This argues for monitoring 3I/ATLAS for as long as possible.

But there might also be light at the end of the tunnel. In case any of the technological objects orbiting the Sun produces light, it might be more detectable than expected from the reflection of sunlight off its surface.

As suggested in a peer-reviewed paper I co-authored with Ed Turner in 2011 (accessible here), it is possible to distinguish a source of artificial light from a natural large rock that reflects sunlight by the fact that its brightness would change inversely with distance square, like the brightness of a light-bulb. On the other hand, an object that reflects sunlight dims inversely with heliocentric distance to the 4th power. Our paper showed that the deepest images from the Hubble Space Telescope would be sensitive to the light produced by a city like Tokyo at the distance of Pluto. Of course, the spectrum of artificial light might deviate considerably from that of sunlight reflected by a rock, offering another way to verify its anomalous origin.

Mike Brown, the pioneering discoverer of many Trans-Neptunian Objects (TNOs) who demoted Pluto’s status as a planet, visited my office at Harvard a decade ago. I used this opportunity to ask Mike whether he checked if the brightness of all TNOs scales inversely with heliocentric distance to the 2nd or 4th power. He replied: “Why would I check… it must be the 4th power.” As often the case in mainstream science, our ability to discover new knowledge is moderated by the arrogance of expertise. Learning requires humility, akin to a beginner’s mind.

If we ever discover an object that produces artificial light, we would be motivated to send our own spacecraft out there and answer Fermi’s question from up close. I would be the first in line to board that spacecraft.

ABOUT THE AUTHOR

(Image Credit: Chris Michel, National Academy of Sciences, 2023)

Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.

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