Observations from the Subaru Telescope show chemical variation in comet 3I/ATLAS after solar approach

The Telescópio Subaru equipment collected unprecedented data on the interstellar comet 3I/ATLAS during the months of December 2025 and January 2026. The analyzes indicate a significant change in the proportion of carbon dioxide in relation to water in the gas cloud that surrounds the celestial body. Essa chemical variation occurred shortly after the object reached the point of greatest proximity to Sol. The celestial body represents the third confirmed visitor from outside our solar system.

The object’s passage offers a rare opportunity for the scientific community to study materials formed in other regions of the galaxy. The heating caused by the central star of our system triggered physical reactions on the comet’s surface. Pesquisadores monitor the evolution of the coma to understand the internal structure of the visitor. The hyperbolic trajectory confirms that the body does not orbit Sol and will return to deep space.

Operação of optical instruments and spectrographs in Havaí

The team of astronomers used the FOCAS spectrograph and imager coupled to Telescópio Subaru to record precise images in the V, R and I bands. The main capture took place on December 13, 2025, following the Havaí time zone. The instrument produced detailed color composites from the observed wavelengths. The V band, centered at 550 nanometers, represented the color blue. The R band, operating at 660 nanometers, generated the color green. Band I, at 805 nanometers, defined the red tones. The processing revealed complex structures in the comet’s tail.

The Espectrógrafo of Alta Dispersão went into operation on January 7, 2026 to measure gas emissions. The comet was 2.87 astronomical units away from Sol at this specific time. One astronomical unit is equivalent to the average distance between Terra and Sol, around 150 million kilometers. The object was already moving away from the star after crossing perihelion on October 29, 2025, when it reached 1.35 astronomical units. Observations took place during morning twilight. The short exposure time required high sensitivity of the optical sensors.

Dinâmica sublimation and the proportion of volatile compounds

Scientists calculated the ratio between carbon dioxide and water with values ​​ranging between 0.3 and 2.1 based on information from terrestrial equipment. Previous Medições images taken by infrared space telescopes indicated a higher concentration of carbon dioxide before Sol’s closest approach. The discrepancy in the numbers proves that the mixture of gases released by the nucleus is not constant. Carbon dioxide sublimates at temperatures considerably lower than water. The direct transition from the solid to the gaseous state creates the temporary atmosphere around the nucleus.

The change in the chemical signature works as a direct indicator of the original environment in which the celestial body was formed. The indices recorded in the post-perihelion phase of 3I/ATLAS were lower than those detected in previous weeks. The phenomenon occurs because solar heat initially consumes the most volatile materials present in the outer crust. Internal and deeper Camadas begin to eject material as surface wear progresses. The mechanism exposes the heterogeneity of the interstellar visitor’s internal structure.

• Monitoring prioritized the gases responsible for driving coma activity.
• The chemical relationship differentiates the compounds on the surface from those housed inside the nucleus.
• Thermal radiation displaces the active gas release zones during the orbital path.
• Information from the ground observatory served as the basis for calibration with satellites.

The detailed analysis of sublimation allows us to draw parallels with the behavior of celestial bodies native to Nuvem and Oort. The process of mass loss alters the comet’s rotation and trajectory at microscopic levels. The ejection of gas jets acts as a natural propellant in the vacuum of space. Continuous monitoring of the water loss rate defines the active lifetime of the object.

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Descoberta on Chile and the nature of the hyperbolic trajectory

The ATLAS warning system, installed on Chile, first identified the comet on July 1, 2025. Orbital analysis quickly confirmed an extreme hyperbolic trajectory. The object’s speed overcomes the gravitational force of Sol, preventing its capture by our planetary system. The astronomical catalog records only three bodies with this characteristic confirmed to date. 1I/’Oumuamua opened the list, followed by comet 2I/Borisov. 3I/ATLAS consolidates the existence of a population of wandering bodies crossing the galaxy.

Interstellar objects deliver physical samples from distant planetary systems directly into the vicinity of Terra. Deep space travel preserves original chemical characteristics for billions of years. Entry into the solar system represents the first intense contact with stellar radiation since the ejection from its home system. The study of the chemical composition facilitates the comparison of planetesimal formation processes in different arms of Via Láctea. Astronomy gains practical tools to test theoretical models of stellar evolution.

The visitor reached the minimum distance from Terra on December 19, 2025. The comet passed approximately 1.8 astronomical units from our planet, the equivalent of 270 million kilometers. The position in the sky limited the observation window for ground-based telescopes during the brightest period. The celestial body maintains its exit route towards interstellar space. Research stations continue to track the weakening of the light signal.

Metodologia research and advancement in the study of comets

Researcher Yoshiharu Shinnaka, linked to Universidade Kyoto Sangyo, led the team responsible for processing the data. The group applied the same mathematical protocols used in the study of local comets to analyze the interstellar target. Methodological standardization guarantees precision in direct comparison between bodies of different origins. The results highlight unexpected structural similarities alongside fundamental chemical differences. The unified approach eliminates error variables in the interpretation of light spectra.

The entry into operation of new astronomical complexes in the next decade promises to increase the detection rate of external visitors. The increase in data volume will allow the creation of specific taxonomic categories for interstellar objects. Cada new passage provides additional pieces to the puzzle of galactic chemical diversity. The work performed with the Telescópio Subaru sets a standard of excellence for future fast target observation campaigns. Optical instrumentation proves its ability to operate at the limit of technical sensitivity.

The database generated by the 3I/ATLAS passage reinforces the need for prolonged monitoring throughout the entire visible orbit. The information feeds computer simulations about the clumping of dust and ice in the orbit of young stars. The comet delivers raw data on particle physics in extreme microgravity environments. Systematic observation documents the physical degradation of the core under thermal stress. The scientific record remains active as long as the equipment can capture the photons reflected by the distant coma.