Linking the Non-Gravitational Acceleration of 3I/ATLAS to Its Symmetric System of Three Jets
A new paper (accessible here) that I co-authored today with Toni Scarmato analyzed images of the interstellar object 3I/ATLAS, taken by the Hubble Space Telescope over the past five months. After removing the circularly-symmetric glow around the nucleus of 3I/ATLAS using the Larson-Sekanina rotational gradient filter, we identified three jets emanating from the nucleus that are equally separated from each other in sky projection by about 120 degrees in addition to a primary anti-tail jet pointed at the Sun.
Whether these jets are technological thrusters or pockets of ice that happened to be oriented symmetrically on the surface of a natural iceberg, the outflows of gas and dust in these three jets exerted thrusts through the rocket effect, which resulted in the observed non-gravitational acceleration of 3I/ATLAS (as summarized in a paper that I co-authored with Valentin Thoss and Andi Burkert, accessible here). Our new paper links, for the first time, the directions and momentum flows in these three jets to the non-gravitational acceleration of 3I/ATLAS.
In our previous paper (accessible here), we demonstrated that the jet system wobbles with a period of 7.2 hours, likely as a result the rotation of the nucleus. We concluded that the jet structure wobbles around the rotation axis with a characteristic angular excursion of about 20 degrees, and the rotation axis is aligned with the sunward direction to within about 20 degrees.
Building on this inferred jet system and periodic wobble analysis of 3I/ATLAS, our new paper measures the observed jet position angles and links them to the non-gravitational acceleration components in three dimensions. We use the sky projection and images of the three persistent jets to estimate the order-of-magnitude thrust that each of them provides to the nucleus. Altogether, our analysis provides consistency between the properties of the three jets and the inferred non-gravitational acceleration of 3I/ATLAS, strengthening the evidence that the rocket effect explains the deviations of its trajectory from the path expected from gravity alone.
We adopted the observed jet position angles (PAs) in the sky (with North=0◦, East=90◦) on November 30, 2025 as follows:
• Jet1: PA = 65◦, • Jet2: PA = 290◦, • Jet3: PA = 175◦.
Our analysis identifies Jet2 as the dominant contributor to the transverse non-gravitational acceleration. The table below shows the breakdown of the contributions from the three jets to the non-gravitational acceleration of 3I/ATLAS, a [with components (A1,A2,A3)], in meters per second squared:
The complete set of Hubble Space Telescope (HST) images is available here.
The symmetric configuration of three jets plus the anti-tail jet raises the question of whether they might constitute a technological system designed for stabilizing the trajectory of 3I/ATLAS. A recent paper by Bo Andree (accessible here) suggested that the minimal approach for steering an interstellar comet along a controlled trajectory indeed matches this 3+1 jet configuration. By relaxing the full six-degree-of-freedom control to forward-cone steering — sufficient for practical navigation — the paper showed that four thrusters are required: one primary jet and three secondary jets separated symmetrically by 120 degrees from each other. The secondary 3-jets synthesize continuous in-plane steering, while the primary jet provides attitude shaping: as the body rotates, the primary-jet torque direction sweeps predictably over a cycle, enabling out-of-plane steering via phase-scheduled firing.
This highlights the fundamental question: is the observed 3+1 jet system around 3I/ATLAS a technological signature?
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, former director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics (2005–2026), 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.
Professional website:
https://lweb.cfa.harvard.edu/~loeb/
Social media:
https://avi-loeb.medium.com/
https://www.youtube.com/@ProfessorAviLoeb
https://open.spotify.com/show/1zhndXkvSY2b8FdjspFpCd
https://x.com/ProfAviLoeb
