The third interstellar object confirmed to visit Sistema Solar showed significant changes in its chemical composition shortly after passing through the closest point to Sol. Observações performed in January 2026 by Telescópio Subaru, located at Mauna Kea, at Havaí, revealed that the proportion of carbon dioxide to water in the gases released by the coma decreased considerably after perihelion. Comet 3I/ATLAS, also designated C/2025 N1 (ATLAS), follows a hyperbolic trajectory and has no gravitational connection with Sol, ensuring its return to interstellar space.
Telescópio Subaru captures details of post-periile coma
The Hawaiian equipment, equipped with a main mirror with an effective diameter of 8.2 meters, carried out the measurements on January 7, 2026. The images combined data from three different optical filters: V (550 nanometers), R (660 nanometers) and I (805 nanometers). Essa multi-filter approach allowed astronomers to accurately analyze the proportion of gases released by the coma at different wavelengths. The results indicate that the ratio between CO₂ and H₂O in gases was significantly lower than previous records obtained by space observatories before Sol’s closest approach.
The observed difference points to substantial changes in the nucleus’ activity as the object progressively heated. Conforme the solar temperature increased during the approach, the sublimation behavior of the ices changed, exposing deeper layers of the cometary nucleus. Esse process confirms that the internal structure is not uniform, but presents compositional variations between different depths.
Layered Estrutura explains variations in outgassing
Camadas outside the core releases more volatile compounds at lower temperatures. As solar heating progressively removes the surface layers, the internal material, with different chemical proportions, begins to dominate the release of gases. Materiais more volatile compounds, such as certain compounds rich in carbon and oxygen, sublime before less volatile components. Essa feature reflects fundamental differences between the surface and inner layers of the cometary nucleus.
Comet 3I/ATLAS reached perihelion in October 2025, approaching Sol at a distance of about 1.36 astronomical units. Durante throughout the approach, maintained safe distances from planets like Marte, Vênus and Terra. The hyperbolic trajectory guarantees that the object will continue its path out of Sistema Solar after this visit, without risk of impact with any celestial body.
Descoberta and context of interstellar visitors
3I/ATLAS represents the third object confirmed as interstellar to cross Sistema Solar. The previous ones were 1I/’Oumuamua, detected in 2017, and 2I/Borisov, observed in 2019. Diferente of the first two, this object behaves like an active comet, releasing dust and gases as it approaches Sol. The initial discovery occurred on July 1, 2025, at Chile, via the ATLAS system. The velocity and hyperbolic trajectory quickly confirmed its origin outside of Sistema Solar.
- Observações combined three filters allowed mapping the coma at different wavelengths with high precision
- Análise focused on the ratio of CO₂ to H₂O in the gases released by the nucleus
- Resultados indicate layered structure in interstellar comet nucleus
- Compositional Mudança occurred due to progressive heating during solar approach
- Dados will be published in the The Astronomical Journal magazine in the coming weeks
Scientific Importância for Understanding Stellar Systems
The study of the coma allows access to information about the interior of the nucleus without direct contact. The change in the proportion of gases reflects how solar heating affects different materials over time, offering clues about the chemical conditions in the comet’s home star system. Comparações with comets from Sistema Solar show that objects formed in other stellar systems can have different compositions, contributing to the understanding of processes that occur in cometary nuclei of interstellar origin.
Pesquisadores highlight that objects like 3I/ATLAS carry material formed billions of years ago, possibly in older regions of Via Láctea. Comparison with local comets helps map differences in planetary formation processes in different cosmic environments. The Telescópio Subaru results contribute to models that describe the evolution of cometary nuclei under stellar influence, expanding knowledge about the primordial matter of different regions of the galaxy. The comet will continue to move away and, in a few thousand years, will completely leave the surroundings of Sistema Solar, ending this rare observation opportunity.
