Interstellar comet 3I/ATLAS displays longer, brighter tail in recent observations
Robotic telescopes on Projeto Telescópio Virtual have captured images of comet 3I/ATLAS that reveal its ionic tail is longer and brighter than in previous records. The object, discovered in July 2025 in Chile by the ATLAS system, originated outside of Sistema Solar and follows a hyperbolic trajectory. Astrônomos observe the phenomenon in November 2025, when the comet moves away from the perihelion reached on October 29th.
The expansion of the tail results from interaction with solar radiation, which releases gases and dust from the icy core. Especialistas confirm that the comet does not pose a risk to Terra, maintaining a minimum distance of 270 million kilometers in December.
- Initial discovery on July 1, 2025 by ATLAS telescope at Río Hurtado.
- Third confirmed interstellar object, after ʻOumuamua and Borisov.
- Estimated age between 3 and 11 billion years, older than Sistema Solar.
Origin and initial detection
Comet 3I/ATLAS entered Sistema Solar at a speed of about 61 km/s, initially detected in pre-discovery observations from June 2025. Astrônomos of Instituto of
The hyperbolic trajectory, with a low inclination in relation to the ecliptic, differentiates it from local comets and suggests ejection from another stellar system billions of years ago.
Chemical composition revealed
Data from Telescópio Espacial James Webb, obtained in August 2025, identified carbon dioxide, carbon monoxide and water ice in the core.
The presence of carbonyl sulfide points to its formation in an ancient galactic region, possibly in the thick disk of Via Láctea.
This composition differs from solar comets, with a greater abundance of volatiles that evaporate under solar radiation, contributing to the tail’s current brightness.
Research indicates that the nucleus measures between 3 and 11 kilometers in diameter, releasing dust grains that form the observed structure.
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Space mission observations
NASA and ESA missions captured data during the close pass of Marte on October 3, 2025, 28 million kilometers away.
The MAVEN probe recorded hydrogen atoms in September, confirming the release of interstellar gases.
Intersections with active probes
The tail of 3I/ATLAS crossed the paths of probes such as Europa Clipper and Hera between October 30 and November 6, 2025.
Astronomers at Sociedade Astronômica Americana published simulations in October, predicting the event as a unique opportunity for in situ analysis.
This coincidence allowed measurements of dust and ions without direct intervention, improving models of cometary dynamics.
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The crossing occurred 29 million kilometers from Marte, without interfering with mission operations.
Tail activity and evolution
Observations of Hubble in July 2025 showed initial jets of material, evolving into a broad 3-arcsecond tail.
The reddish color of the coma, similar to comet Borisov, indicates fine dust blown by solar pressure.
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In November, ESA’s JUICE probe analyzed the object between the 2nd and 25th of the month, using spectrometers to map compounds.
Early outgassing, detected by TESS in May 2025, suggests warming of ice grains to 6.4 astronomical units of Sol.
Future trajectory and visibility
The comet heads to the constellation Gêmeos in 2026, shining below magnitude 12 in December 2025.
Ground-based telescopes follow the object until spring 2026, when it will leave the field of view.
Its speed relative to Sistema Solar, above 137 thousand km/h, confirms an interstellar origin without gravitational capture.
Implications for galactic studies
Analysis from July 2025 estimates an age of 7.6 to 14 billion years, based on stellar populations from the thick disk.
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The object carries traces of distant planetary formation, with low metallicity compared to Sol.
Researchers predict that Telescópio Vera C. Rubin will enhance future detections of interstellar visitors.
