Astronomers using the Hubble Space Telescope have captured unprecedented images of the third known interstellar object, 3I/ATLAS, as it passes through our solar system. The object exhibits comet-like activity at an unusually large distance from the Sun, providing valuable insights into the composition and behavior of visitors from other star systems.
In July 2025, the Hubble Space Telescope captured detailed images of 3I/ATLAS, the third interstellar object observed passing through our solar system. The observations, published on August 12-13, 2025, reveal the object displaying comet-like features including a dust plume and a faint tail. This activity was detected while the object was 3.8 astronomical units (AU) from the Sun—nearly four times the Earth-Sun distance—which is unusually far for such activity.
The discovery and analysis were led by David Jewitt from UCLA, using the Hubble Space Telescope’s Wide Field Camera. The team tracked 3I/ATLAS as it approached the Sun, measuring its dust emissions and tail formation. Hubble’s high resolution allowed astronomers to estimate the object’s dust-loss rate (6-60 kg/s) and constrain the size of its nucleus (less than 2.8 km in radius, assuming low reflectivity).
3I/ATLAS is only the third confirmed interstellar visitor, following ʻOumuamua (2017) and 2I/Borisov (2019). Its activity at 3.8 AU challenges existing models of cometary behavior, as typical solar system comets become active closer to the Sun (2-3 AU). This suggests 3I/ATLAS contains highly volatile ices (like carbon monoxide) that sublimate at lower temperatures, or has an unusually dark surface absorbing more heat.
Preliminary analysis indicates the object’s activity may be driven by sublimating carbon monoxide or other volatiles. The absence of cyanogen (common in solar system comets) and presence of hydroxyl (indicating water) in other studies hint at a distinct composition shaped in a different stellar environment. Each interstellar object carries chemical signatures from its home system, offering clues about planet formation elsewhere in the galaxy.
Studying 3I/ATLAS helps refine theories about planetary system formation and material exchange between stars. Its unexpected activity at great solar distance suggests interstellar objects may be more dynamic than previously thought, potentially revising how astronomers model comet behavior in alien systems.
3I/ATLAS will reach perihelion (closest approach to the Sun) in October 2025 at 1.5 AU. Astronomers worldwide will monitor it intensively using ground and space telescopes to analyze changes in activity and composition. While too fast for a spacecraft rendezvous, future missions could target similar objects to directly sample interstellar material.
These observations underscore Hubble’s ongoing role in interstellar research and highlight the need for dedicated surveys (e.g., the Vera C. Rubin Observatory) to detect more such visitors. Understanding 3I/ATLAS contributes to the emerging field of interstellar object characterization, paving the way for deeper insights into galactic evolution.
The detailed study of 3I/ATLAS marks a leap in our ability to analyze interstellar objects, transforming them from fleeting curiosities into rich sources of cosmic knowledge.