Comet 3I/Atlas, detected on July 1, 2025 by the ATLAS telescope at Chile, represents the third interstellar object confirmed to cross Sistema Solar. Astrônomos from NASA and international agencies have been monitoring its passage since then, with intensified observations in November 2025. The hyperbolic trajectory confirms its external origin, with no orbit linked to Sol.
Its initial speed of 61 km/s and acceleration to 57 km/s in addition to solar influence highlight dynamic peculiarities. Equipes global companies use ground and space telescopes to record data before it is definitively released.
The chemical composition, revealed by spectroscopic analyses, differs from local comets, with an emphasis on high carbon dioxide. Esses findings arise from missions such as James Webb and Hubble, which captured gaseous emissions in August and September 2025.
Global monitoring reveals details of the 3I/Atlas structure
NASA equipment captured images of the comet from multiple perspectives as it approached perihelion on October 30, 2025.
The MAVEN mission, orbiting Marte, recorded hydrogen atoms around the object on September 28, 2025, 30 million kilometers from the red planet.
The Perseverance rover identified the comet as a faint glow on October 4, 2025, confirming its remote visibility.
These observations, combined with data from SOHO between October 15 and 26, 2025, provide the broadest picture to date.
Chemical composition differentiates 3I/Atlas from solar objects
On August 6, 2025, Telescópio James Webb detected a coma dominated by carbon dioxide, with a proportion eight times greater than the water observed in comets from Sistema Solar. Essa anomaly suggests formation in cold regions of another protoplanetary disk, possibly at the CO₂ ice line.
Carbon monoxide and carbonyl sulfide also appear in emissions, indicating prolonged exposure to interstellar radiation. The core, estimated to be between 440 meters and 5.6 kilometers in diameter by Hubble on August 20, 2025, exhibits stable ejections with no flares detected.
- Carbon dioxide (CO₂): Principal component of the coma, above 80% of volatile emissions.
- Water (H₂O): Baixa concentration, suggesting internal barriers to solar heat.
- Carbon monoxide (CO): Presente at moderate levels, compatible with advanced ages.
- Other traces: Cianeto and high deuterium, three times that of Earth’s oceans.
These elements reinforce the hypothesis of an origin system with different thermal conditions.
Origin and estimated age of the cosmic visitor
Computational models indicate that 3I/Atlas formed 7.6 to 14 billion years ago in the thick disk of Via Láctea, a region of old stars with low metallicity. Essa’s age exceeds the 4.6 billion years of Sistema Solar, making it a relic of early galactic eras.
Its likely ejection occurred through gravitational interactions with massive bodies in its home system, directing it into interstellar space. TESS’s Observações suggests cometary activity since May 7, 2025, at 6.4 astronomical units from Sol.
Astronomers like NASA’s Tom Statler describe the object as a time capsule for remote stellar histories. The high vertical velocity in relation to neighboring stars reinforces its inclined orbit in the galaxy.
The rich nickel versus iron composition detected in analyzes from November 2025 supports this narrative of primordial formation.
Tail anomalies and emissions of the 3I/Atlas
On November 5, 2025, NASA recorded an inverted antitail pointing to Sol, an unprecedented phenomenon that lasted days before dissipating. Essa structure, composed of plasma and dust, was replaced by a conventional anti-solar tail of 56 thousand kilometers.
Radio and ultraviolet emissions, generated by interactions with the solar wind, produce regular fluctuations observed by instruments such as Mars Reconnaissance Orbiter’s HiRISE on October 2, 2025.
Extreme polarization in reflected light challenges models of sublimation, suggesting complex internal dynamics. Caudas of dust, visible at Gemini South in August 2025, has grown to 30 arcseconds.
These variations, without visible mass loss, intrigue teams that predict the gravitational influence of Júpiter in March 2026.
Comet trajectory and future observations
3I/Atlas reached perihelion at 1.4 astronomical units from Sol, without risk to Terra, with a minimum approach on December 19, 2025 at 1.8 astronomical units. Sua exit goes beyond the heliosphere, at 50 km/s.
Missions like Psyche and Lucy captured sequences in September 2025, 53 million kilometers away, revealing a halo of gas and dust. JWST plans new observations in December 2025 to map post-perihelion changes.
Ground-based telescopes track the object in the constellation Virgem until spring 2026, with an apparent magnitude of 10. Rede Internacional of Alerta of Asteroides coordinates alerts for precise trajectories.
Scientific implications of the 3I/Atlas passage
The study of the comet expands the understanding of interstellar objects, with possibly underestimated passing frequencies. Suas chemical properties contrast with ‘Oumuamua and Borisov, enriching models of planetary formation.
Hydrogen emissions data from MAVEN in September 2025 illustrate interactions with planetary environments. Astrônomos predict that final spectral analyzes will reveal more about accretion disks in ancient stars.
The observation campaign, involving 20 missions, demonstrates global coordination for rare events. The object, now declining in brightness, will continue to inform simulations of galactic evolution.
