Interstellar Object 3I/ATLAS: Why Hubble’s New 'Double Jet' Discovery Baffles
Images of 3I/ATLAS through 170 second exposures by the WFC3 UVIS (F350LP) camera of the Hubble Space Telescope, processed through the Larson-Sekanina rotation gradient filter, show a double jet structure. Hubble Space Telescope/NASA

NASA scientists are facing questions after the Hubble Space Telescope spotted an unexpected feature on the interstellar object 3I/ATLAS, which was observed releasing two distinct jets of material as it travelled away from the Sun.

The latest images were taken in December 2025, months after the object's closest solar approach, when activity was expected to fade. Instead, the discovery has left researchers reassessing how such rare visitors behave after leaving the inner solar system.

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What the Newly Discovered 'Double Jet' Looks Like and Why It Is Unusual

Hubble observed 3I/ATLAS on 12 December 2025 and again on 27 December 2025, using its Wide Field Camera 3. The instrument captured faint details through 170-second exposures, allowing astronomers to track subtle structures around the object. By this stage, 3I/ATLAS had already passed perihelion in late October 2025, reducing expectations of complex activity.

Instead of a single fading plume, the images revealed two narrow, persistent jets. One appeared stronger and pointed roughly towards the Sun, while a weaker jet emerged from the opposite side.

Harvard astrophysicist Avi Loeb, head of the Galileo Project, said the images showed 'a surprisingly structured scene,' noting that the geometry formed a clear double-jet pattern. The repeated appearance across both December observations confirmed the feature was genuine.

How 3I/ATLAS's Rotation and Solar Heating Complicate Jet Behaviour

Earlier Hubble images from 21 July 2025 had already hinted at unusual behaviour. They observed a sunward jet ten times longer than it was wide, with a seven-degree wobble. That motion suggested the plane was linked to a rotational pole rather than random surface cracks.

As 3I/ATLAS passed the Sun, its trajectory bent by only 16 degrees, according to calculations discussed by Loeb. If the spin axis remained stable, the region once facing the Sun should now lie in darkness.

Yet the December images show continued activity, with jets emerging from both illuminated and shadowed regions, complicating standard expectations.

Why the Jet Geometry Challenges NASA's Standard Comet Models

NASA scientists usually expect comet-like objects to vent material primarily from sunlit areas. Activity from shaded regions is typically weak or absent. With 3I/ATLAS, the weaker jet aligns with a direction that should now be facing away from the Sun. Meanwhile, the stronger jet appears from the opposite side.

This geometry challenges simple outgassing models. The jets are narrow, stable, and persistent, suggesting an organised process linked to rotation and internal structure.

Their consistency across multiple observations has made it difficult to dismiss the behaviour as short-lived or random.

Competing Scientific Explanations for Two Persistent Jets

One explanation remains conservative. Heat absorbed during perihelion could slowly travel through the object, activating vents on the night side. This delayed heating could produce a weaker secondary jet while the sunlit side continues to vent more strongly.

Another possibility is that the object's active regions changed after perihelion. That would point to a complex interior with multiple vents responding differently as the object cooled.

Loeb has also discussed whether different particle sizes could explain the pattern, with larger dust grains forming extended anti-tails while solar forces rapidly redirect smaller particles.

What Future Telescope Data Must Reveal to Solve the Puzzle

Scientists say resolving the mystery will require spectroscopic data, detailed measurements of jet velocities, and continued monitoring of brightness changes. Facilities such as the Keck Observatory and the Very Large Telescope are expected to play a role.

Loeb has linked the jet wobble to a 16-hour brightness variation detected earlier in 2025, suggesting that mass loss may already be altering the object's rotation.

As 3I/ATLAS exits the solar system, it remains a rare opportunity for NASA and its partners to study material formed around another star, and to test how well current models explain the unfamiliar.

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