New astronomical data released by Universidade of Kyoto Sangyo has brought to light unique characteristics about the chemical composition of the interstellar comet 3I/ATLAS. Observations carried out at Japão indicate a significant ammonia deficiency in the object’s structure, differentiating it from most celestial bodies observed at Sistema Solar.
Analyzes were conducted on Observatório Mitayama and focused on spectroscopy of the comet to identify its volatile components. Diferente of local comets, which generally have an abundance of nitrogenous compounds, the interstellar visitor showed an unexpected chemical pattern for scientists.
During monitoring, the instruments detected the presence of several molecules, but the absence of a specific marker caught the researchers’ attention:
– Emissões confirmed diatomic carbon molecules (C₂);
– Presença of triatomic carbon (C₃) and cyanide radical (CN);
– Detecção of atomic oxygen in the comet’s coma;
– Ausência noticeable NH₂ emissions, indicative of lack of ammonia (NH₃).
This chemical configuration suggests that 3I/ATLAS formed in a stellar environment with temperature and pressure conditions different from those that gave rise to our planetary system. The absence of ammonia in the comet’s ice raises questions about the diversity of protoplanetary disks in Via Láctea and provides valuable clues about the distribution of volatile elements in other regions of the galaxy.
Trajectory details and interstellar confirmation
The object was initially identified in July 2025, sparking immediate interest from the global astronomical community due to its hyperbolic orbit. Ele reached perihelion, the point of closest approximation to Sol, on October 29 of the same year, when solar heating maximized the release of gases and dust, facilitating spectral analysis.
After passing close to the star, the celestial body followed an escape trajectory, confirming that it is not gravitationally bound to Sol and that it will leave the system permanently. The interstellar nature of the object was corroborated by complementary observations made by NASA’s Hubble space telescope at the end of November 2025, consolidating 3I/ATLAS as the third confirmed visitor in this category.
The rarity of these events makes each discovery crucial to understanding galactic dynamics. Antes of 3I/ATLAS, only 1I/ʻOumuamua, in 2017, and 2I/Borisov, in 2019, had been cataloged as objects from other stellar systems, offering limited but rich opportunities for study.
Methodology applied in Observatório Mitayama
To unravel the comet’s composition, the team of researchers used Observatório Mitayama’s 1.3-meter telescope over three nights between November and December. The main equipment was the LOSA/F2 spectrograph, configured to capture data in visible light with low dispersion, an ideal technique for identifying gas signatures in fast-moving objects.
The spectral resolution obtained allowed the decomposition of light in sufficient detail to isolate the emission lines of chemical elements. Embora the overall spectrum showed similarities to solar comets at certain wavelengths, detailed analysis revealed the fundamental discrepancy in the region where ammonia should appear.
The NH₂ molecule is typically observed as a byproduct of the photodissociation of ammonia by sunlight. Sua’s lack of evidence in the collected data is the strongest evidence yet that 3I/ATLAS’s core ice is poor in volatile nitrogen, a feature that defies standard models based solely on the chemistry of Sistema Solar.
These data are complemented by information from other observatories and space instruments, such as Telescópio Espacial James Webb (JWST), which have also reported variations in the composition of gases on distant celestial bodies, reinforcing the validity of terrestrial observations made on Japão.
Relevance to planetary formation
Comets are considered fossils of star formation, preserving in their ice the primordial chemical conditions of the cloud of gas and dust that gave rise to their respective systems. Sistema Solar formed approximately 4.6 billion years ago, and its comets reflect the chemistry of that specific time.
By analyzing an object like 3I/ATLAS, scientists have direct access to materials formed in another place and time, possibly around a star with a different metallicity or radiation history. The presence of carbon- and oxygen-based elements, contrasted with the lack of ammonia, indicates that the “recipe” for the formation of planetary systems is not universal.
Responsible team and publications
The study included the active participation of students and renowned experts. Yuki Tsujimoto, a first-year postgraduate student in Ciências Naturais, played a central role in data acquisition and processing, demonstrating the integration of teaching and cutting-edge research at the university.
The project was led by Hideyo Kawabe, main author of the scientific article, with the collaboration of researchers such as Yoshiharu Niinaka, Hitomi Kobayashi and Takafumi Otsubo. The detailed results were accepted for publication in the specialized journal The Astrophysical Journal Letters, ensuring peer review and global dissemination of the findings.
Junichi Watanabe, comet expert appointed to take over direction of Instituto from Ciência Espacial Mitayama in April 2026, highlighted the importance of these discoveries for positioning Sistema Solar in a broader cosmic context. Research funding was made possible by government grants aimed at advancing astronomy.