Observatório Astronômico Nacional of Japão (NAOJ), Agência of Exploração Aeroespacial of Esse object, identified as the third confirmed interstellar, was discovered in July 2025 by the ATLAS system at Chile.
The analyzes focus on the hyperbolic trajectory, gas composition and cometary activity of the celestial body. The studies contribute to the understanding of visitors from outside the Sistema Solar, complementing international observations carried out since the initial detection.
The researchers highlight that the comet has characteristics similar to objects from Sistema Solar, but with an external origin confirmed by its speed and unbound orbit.
Initial discovery and confirmation
The cometC/2025 N1 (3I/ATLAS)it was detected on July 1, 2025 by the NASA-funded ATLAS telescope located at Chile. Initial Observações indicated a hyperbolic trajectory, suggesting an interstellar origin.
The following day, telescopes at different locations confirmed the presence of a coma and an incipient tail, classifying it as a comet. Centro of Planetas Menores assigned the official designation3I/ATLAS, marking it as the third known interstellar object, after ‘Oumuamua and Borisov.
Pre-discoveries extended observations until June 2025, refining orbital calculations. The high eccentricity, greater than 6, confirms that the comet is not gravitationally bound to Sol.
Observations carried out at Japão
Observatório Astronômico Nacional teams on Japão used facilities such as Telescópio Subaru on Havaí to capture detailed images of the comet in December 2025. The photos revealed the ionized tail and complex structures in the coma.
JAXA contributed with analysis of data from satellites such as XRISM, which detected X-ray emissions arising from interaction with the solar wind. Essas observations indicate processes similar to those of solar comets, including release of cyanide and nickel vapor.
Universidade Kyoto Sangyo participated in spectroscopic studies, identifying typical gas compositions. The independent results converge to a unified view of the object’s activity.
Trajectory and orbital characteristics
The comet followed a hyperbolic orbit with perihelion on October 29, 2025, at about 1.36 astronomical units from Sol. The closest passage to Terra occurred on December 19, 2025, at 1.8 astronomical units, without any risk of collision.
The high relative speed, around 57 km/s, positions it as the fastest among known interstellar objects. Estimativas suggests origin in the thick disk of Via Láctea, possibly older than 7 billion years.
- Eccentricity: greater than 6
- Hyperbolic speed: about 57 km/s
- Minimum distance to Sol: 1.36 AU
- Minimum distance to Terra: 1.8 AU
These parameters highlight the unbound nature of the object.
Composition and cometary activity
Spectroscopic observations revealed emissions of cyanide and atomic nickel, in concentrations comparable to those of Sistema Solar comets. The presence of a diffuse coma and ionized tails confirms activity due to ice sublimation.
Telescopes such as the Very Large Telescope and Hubble captured details of the cloud of dust and gas surrounding the nucleus, estimated to be between 0.6 and 5.6 km in diameter. The reddish color of the coma indicates the presence of organic dust.
X-ray studies, including Japanese contributions, have detected interactions with the solar wind, generating characteristic emissions. Esses data suggests that the comet transports primitive materials from another star system.
Comparison with previous interstellar objects
Unlike ‘Oumuamua, which showed no visible cometary activity, the3I/ATLASexhibits clear coma and tails, similar to 2I/Borisov. However, its speed and eccentricity are superior, making it unique.
The greater brightness and size facilitated detailed observations compared to predecessors. Pesquisas indicate possible advanced age, offering clues about planetary formation in the galaxy’s ancient environments.
- ‘Oumuamua (1I): no coma, elongated shape
- Borisov (2I): moderate cometary activity
- ATLAS (3I): complex tails, high speed
This comparison reinforces the diversity among interstellar visitors.
Recent scientific contributions
Japanese research complements global data from missions such as Hubble, Lucy and Psyche, which captured images in different phases. Análises of non-gravitational acceleration attribute variations to the release of gases.
The comet remained observable until the end of 2025, with its current position in the constellation Leão. Estudos continue to refine source and composition models.
International teams, including Japanese ones, have published results that enrich knowledge about interstellar matter. The rarity of these events drives collaborations for future detections.