The interstellar comet3I/ATLASreaches this Friday, December 19th, the point of closest approximation toEarth, about 270 million kilometers away. Esse rare visitor, originating from another star system, poses no risk of collision and offers a unique opportunity for detailed scientific observations.
Discovered on July 1, 2025 by the ATLAS telescope at Chile, the object was quickly confirmed as the third interstellar detected, after ‘Oumuamua (2017) and Borisov (2019). Sua hyperbolic trajectory indicates that it will leave Sistema Solar permanently after passing.
Telescopes like the Hubble captured images revealing the coma and tail, while spectroscopic analyzes identify a composition rich in ice and dust.
Origin and trajectory of the visitor
3I/ATLAS formed in another planetary system, possibly billions of years ago. Estudos suggests an age between 7.6 and 14 billion years, higher than the 4.6 billion of Sistema Solar.
Its orbit indicates its origin in the thick disk of Via Láctea, with old stars and low metallicity.
- Speed exceeded 221 thousand km/h at discovery.
- Perihelion occurred in October 2025, 210 million km from Sol.
- After approaching Terra, it heads out of the system.
This data is based on observations from ground-based and space-based telescopes, including pre-discoveries since May.
ATTENTION!
— JAMES WEBB (@jameswebb_nasa)December 19, 2025
Interstellar comet 3I/ATLAS makes its closest approach to Terra this Friday (19).
And you can watch it live.
The interstellar comet 3I/ATLAS reaches its closest approach to Terra in the early hours of this Friday, December 19th, according to calculations by Jet…pic.twitter.com/HZRqinZSev
Observed characteristics
The nucleus measures between 600 and 800 meters in diameter, surrounded by a reddish coma that evolved during the solar approach.
Cometary activity began early, at 6.4 AU from Sol, with sublimation of ice forming a tail opposite the star.
Observations detected:
- X-ray emissions → due to interaction with solar wind.
- Color change in coma → indicating release of gases such as diatomic carbon.
- Absence of intense outbursts → maintaining stable brightness.
Images of Hubble in November show a teardrop-shaped structure with dust and gas.
Speculations and scientific consensus
Some observations, such as the release of material in the direction of Sol, generated hypotheses of artificial origin. Cientistas from NASA and ESA dismiss this idea, stating that the object exhibits behavior typical of a natural comet.
Anomalies are explained by different composition of solar comets. The consensus reinforces that it is a pristine body from another system.
Observation opportunities
The comet remains visible with amateur telescopes in the pre-dawn sky until spring 2026. The close approach facilitates detailed captures by instruments such as Hubble and XRISM.
- NASA missions recorded the object from multiple angles.
- Data collected will help understand planet formation in distant systems.
3I/ATLAS highlights advances in telescopes that allow us to detect more interstellar visitors in the coming years.
