Since it was detected crossing the solar system, the interstellar object 3I/ATLAS has become a unique opportunity to observe, almost in real time, how a visitor from another star behaves. And one of the most striking surprises is that his trajectory has not remained fixed: As astronomers have followed it, its course and speed have changed measurably.
When 3I/ATLAS was discovered, calculations showed a clearly hyperbolic orbit, the unmistakable sign that it is not gravitationally bound to the Sun. And, at the same time, an extraordinary speed: At its closest approach to the Sun it reached about 246,000 kilometers per houran impossible figure for an object born in the solar system and one of the proofs of its interstellar origin.
However, something began to catch the attention of scientists as tracking became more precise: the comet was no longer exactly where purely gravitational models predicted it should be. In other words, 3I/ATLAS was deviating slightly from its intended path.
The change is small in absolute terms, but huge from a scientific point of view. Observations indicate additional acceleration, not explainable only by the Sun’s gravity, approximately one ten-thousandth of a millimeter per second squared. It may seem insignificant, but accumulated over days and weeks it is enough to modify its trajectory in a way detectable from Earth.
The most likely cause? The same mechanism that acts in classic comets, taken here to the extreme: the expulsion of gas and dust when the object heats up as it approaches the Sun. This jet acts as a small engine, a “rocket” effect that pushes the comet and alters both its speed and direction. Models suggest that during perihelion, 3I/ATLAS could have lost more than 10% of its mass, a huge number for a solid body traveling alone through interstellar space.
This push not only accelerates it slightly outward, but also introduces a transverse change in its movement: its course was “twisted” with respect to the initial trajectory, forcing predictions of where it will exit the solar system to be readjusted. It is not that it will radically change its destination (it will continue to escape), but the detail matters because it reveals what these objects are like on the inside.: how much ice they conserve, what type of compounds sublimate and to what extent they survive passage near a star.
The future adds another element of uncertainty. Current simulations indicate that 3I/ATLAS could have a relatively close encounter with Jupiter in the coming months, more precisely in March 2026when it will approach about 21 million kilometers, far from the best-known moons of the solar system giant, but half the distance of some of the most distant and irregular ones, many of them part of the Himalia group.
Although a collision or capture is not expected, The planet’s enormous gravity could introduce new disturbances in its trajectory, complicating its exit path.
Deep down, what we are seeing with 3I/ATLAS is something exceptional: The living dynamics of an object from another star system, reacting to the heat of the Sun, losing mass and adjusting its course while telescopes observe it. It is not a cold bullet passing through the solar system, but an active, changing body that offers us a unique opportunity to understand how messengers between stars travel, and how they age.