The interstellar comet 3I/ATLAS, discovered in July 2025 by the ATLAS system in Chile, continues to attract attention from the scientific community even after its closest passage through Terra, on December 19, 2025, at approximately 270 million kilometers. The object, classified as C/2025 N1 (ATLAS), follows a hyperbolic trajectory that takes it outside Sistema Solar, approaching Júpiter scheduled for March 16, 2026. Astrônomos from several global institutions follow its evolution, revealing details about composition and behavior that differ from local comets.
The interstellar visitor stood out for its intense activity during perihelion, which occurred on October 29, 2025, approximately 210 million kilometers from Sol. Observações with telescopes such as Hubble, James Webb and instruments on the ground confirmed the presence of an extensive coma and visible tail, with emissions of gases such as carbon dioxide in high proportions. The discovery came at an opportune time, as the newly operational Observatório Vera C. Rubin captured images of the comet days before official identification, demonstrating the potential for future detections of similar objects.
Details of the discovery and trajectory
The comet was initially identified as a possible asteroid, but rapid observations revealed marginal coma and tail-like elongation, confirming its cometary nature. Minor Planet Center was assigned the designation 3I, marking it as the third confirmed interstellar object after 1I/ʻOumuamua and 2I/Borisov. Sua hyperbolic velocity indicates an origin outside of Sistema Solar, probably from a region with older stars, which suggests an age greater than billions of years.
During its passage close to Sol, 3I/ATLAS exhibited accelerated brightness and a bluish color, attributed to the sublimation of volatiles. Múltiplas space missions, including Parker Solar Probe, Psyche, and probes at Marte, have captured supplementary data. ESA’s Juice probe carried out observations in November 2025, with data expected in February 2026 due to thermal constraints.
Chemical composition and recent observations
Spectroscopic analyzes indicate a composition rich in carbon dioxide, carbon monoxide and traces of cyanide and atomic nickel, common elements in comets, but with proportions that intrigue researchers. The core has an estimated diameter of between 440 meters and 5.6 kilometers, making it the largest interstellar object known to date. Atividade post-perihelion included asymmetric jets and anti-tail oscillations, observed in December 2025.
Searches for artificial signals, carried out with telescopes such as Green Bank, did not detect anomalous emissions, reinforcing the natural classification of the object. The comet remains visible in the pre-dawn sky until spring 2026, albeit at fainter magnitudes, accessible to medium telescopes.
Perspectives for future studies
The passage of 3I/ATLAS represents a unique opportunity to analyze primordial material from another star system. Observatório Vera C. Rubin, with its broad survey, is expected to dramatically increase the number of detections of interstellar objects in the coming years, possibly identifying dozens of similar visitors. Essas observations contribute to understanding chemical diversity in Via Láctea and improving planetary defense models.
The comet is now moving away towards interstellar space, leaving a legacy of data that will continue to be analyzed for years. Sua journey reinforces the importance of continuous monitoring of the sky to capture rare phenomena.
