Comet 3I/ATLAS of interstellar origin is monitored by the UN warning network without risk to Earth
The Rede Internacional of Alerta of Asteroides (IAWN), linked to the Organização of the The object, discovered in July 2025 by the ATLAS system in Chile, follows a hyperbolic trajectory and will reach its closest proximity to Terra on December 19, at around 270 million kilometers. Não there is any risk of collision, as confirmed by experts from NASA and the IAWN network.
The monitoring involves telescopes on several continents and represents the first monitoring of an interstellar object by IAWN since its creation in 2017. The campaign, which runs from November 27, 2025 to January 27, 2026, is halfway through its planned period. The data collected will make it possible to improve astrometry techniques for diffuse celestial bodies such as comets.
- Discovered on July 1, 2025 with cometary activity detected since May.
- Perihelion reached in October 2025, 210 million kilometers from Sol.
- Composition with high concentration of carbon dioxide and spiral structures observed.
- Trajectory includes passes close to Marte, Vênus and Júpiter.
Astronomers record an increase in the comet’s brightness after perihelion, with images revealing more defined coma and tails. Observatórios as Gemini Norte, in Havaí, captured details of cryovolcanic activity suggested by spiral jets.
Interstellar origin of 3I/ATLAS
3I/ATLAS is the third object confirmed to come from outside Sistema Solar, after ‘Oumuamua and 2I/Borisov. Sua high speed and hyperbolic orbit indicate that it was ejected from another star system billions of years ago. Estudos estimate that the comet could be more than 7 billion years old, surpassing the age of our Sistema Solar.
Spectroscopic analyzes reveal a composition rich in CO₂, with eight times more carbon dioxide than water, something rare in local comets.
International campaign coordination
NASA coordinates the actions of IAWN, which brings together more than 80 professional and amateur observatories. The initiative tests methods for measuring precise positions of comets, whose comas and tails make orbital calculations difficult. James Bauer, principal investigator, highlights the unprecedented nature of the exercise with an interstellar object.
Telescopes at Havaí, Chile, and Austrália calibrate algorithms to reduce uncertainty in hyperbolic trajectories.
Challenges in observing comets
Comets have variations in brightness and diffuse structures that complicate astrometry compared to point asteroids. 3I/ATLAS exhibited early activity, detected at large distances from Sol, and changes in coma as it approached perihelion.
These characteristics require advanced techniques to define the core center and accurately predict movements.
Observed physical characteristics
Composite images show spiral jets suggesting cryovolcanism, with ionic and dust tails forming. The estimated core varies between hundreds of meters and a few kilometers in diameter. Observações of Telescópio Espacial Hubble and Gemini reveal an initial reddish color evolving to greener tones.
- Activity detected by probes such as ESA’s JUICE in November.
- Brightness increased significantly post-perihelion.
- Antitail and multiple jets recorded in deep images.
- Composition indicates formation in a cold environment of another system.
Participation of global observatories
More than 80 facilities participate, including professionals and citizen scientists. The campaign planned since 2024 coincided favorably with the comet’s arrival. Dados will be analyzed for publication in scientific journals in 2026.
Records include prediscovery in June and continuous observations through January.
Preparation for future objects
The exercise strengthens tracking capabilities for rare interstellar visitors. Refined Técnicas can help plan space missions to similar comets. The extended visibility of 3I/ATLAS provides a unique opportunity to calibrate instruments.
Experts predict detection of more interstellar objects with new telescopes like Vera C. Rubin.
Trajectory and safe distances
The comet passed 28 million kilometers from Marte in October and will approach Júpiter in March 2026. The minimum distance to Terra on December 19th allows detailed observations without threats.
Advances in cometary astrometry
Researchers test new method for calculating trajectories of objects with variable comas. The fluctuating brightness and expansion of the gas cloud defy traditional measurements. Resultados will improve predictions for NEOs and long-period comets.
The campaign represents IAWN’s eighth exercise since 2017.
Recent images of the comet
Records from November and December show green coma and snaking tails deflected by the solar wind. Telescópios Earth- and space-based bodies have captured detailed post-perihelion structures. The comet reappeared visible after solar conjunction in October.
Amateur observations with modest equipment record the object in constellations such as Leão.
