An interstellar object designated 3I/ATLAS has been observed accelerating unexpectedly as it moves away from the sun and draws closer to Earth, challenging gravitational predictions. The object reached perihelion on October 29, 2025, and is now six weeks from its closest approach to Earth. NASA scientists and astronomers tracking the phenomenon note its deviation from expected trajectories despite the sun’s dominant gravitational influence.
3I/ATLAS, initially recorded as the fastest space object entering the solar system at over 130,000 mph, has since increased its speed to approximately 152,000 mph after passing perihelion. While NASA attributes this acceleration primarily to the sun’s gravity, the object’s noticeable shift from its predicted path remains unexplained.
Harvard physicist Avi Loeb highlighted that astronomers have not detected sufficient gas emissions from the object, which would typically indicate a cometary nature. “If 3I/ATLAS is not enshrouded in a much more massive gas cloud after perihelion than it had in the months preceding perihelion, then its recent non-gravitational acceleration must have resulted from a different cause than cometary evaporation,” Loeb stated.
The object has exhibited unusual characteristics, including a blue hue as it approached the sun—contrary to the red color typical of comets—and an estimated mass of 33 billion tons composed of nickel and carbon dioxide, differing from the ice and water found in solar system comets. These anomalies have led some, including Loeb, to speculate that it could be a nuclear-powered “mothership” of extraterrestrial origin.
NASA’s latest data indicates the mysterious force acting on 3I/ATLAS has weakened since its perihelion passage but remains detectable. The James Webb Space Telescope is scheduled to observe the object in December to search for gas clouds that might explain its movements. However, Loeb and others continue to question whether its behavior and composition suggest a non-natural origin.
