Comet 3I/ATLAS, the third confirmed object of interstellar origin to visit the solar system, passed its closest approach to Terra on December 19, 2025. Observações initials suggest that its age varies between 8 and 14 billion years, which would make it older than Sol, formed around 4.6 billion years ago.
Astronomers from several institutions analyzed the hyperbolic trajectory and speed of the object, which indicate an origin outside the solar system. Dados from Telescópio Espacial James Webb and from ground-based observatories revealed a distinct chemical composition, rich in carbon dioxide, nickel and iron.
The discovery occurred in July 2025 by the ATLAS system, and the comet reached perihelion in October of the same year. Desde then, the object gradually moves away, providing valuable data about ancient cosmic environments.
Theoretical research based on the comet’s speed points to formation in the thick disk of Via Láctea, a region with older stars. Essa feature reinforces the high age estimate compared to local comets.
Interstellar origin of 3I/ATLAS
3I/ATLAS follows a hyperbolic trajectory, confirming that it is not gravitationally bound to Sol. Essa orbit indicates that the object entered the solar system from interstellar space and will continue its journey outward after passing.
Unlike comets originating from Nuvem of Oort or Cinturão of Observações confirmed that it moves at more than 200 thousand kilometers per hour in relation to galactic rest.
Unique chemical composition
Observations of Telescópio Espacial James Webb identified a high concentration of carbon dioxide in the comet. Essa abundance suggests formation in a cold environment, far from its original star, typical of the outer regions of ancient planetary systems.
Atomic emissions of nickel and iron also stand out, characteristics that are rare in comets in the solar system. Essas differences reveal chemical conditions from the galaxy’s earliest ages.
The comet exhibited an initial fan-shaped coma oriented towards Sol, evolving into a distinct tail near perihelion. Jatos oscillations were detected on seven separate nights, changing every seven hours and forty-five minutes.
Trajectory and recent observations
3I/ATLAS was monitored for 37 nights between July and September 2025, using Telescópio Gêmeos of Dois Metros in Observatório Teide, in Tenerife. Essas sessions captured the evolution of the coma and the emergence of jet-like structures.
The core’s rotation period was estimated to be about 15.5 hours. Imagens of Observatório Gemini North, released in December 2025, showed a characteristic greenish glow.
The object reached its minimum distance from Sol in October 2025, at around 1.4 astronomical units. The approach of Terra occurred on December 19, approximately 167 million kilometers away.
Observatories such as Agência Espacial Europeia’s XMM-Newton recorded the comet in X-rays in December 2025. Essas observations complemented optical and infrared data.
Old Age Estimates
The high speed of 3I/ATLAS allowed initial theoretical calculations soon after discovery. Equipes of Universidade of Canterbury, in partnership with Universidade of
This age group associates the comet with the thick disk of Via Láctea, a stellar population older than the thin disk where Sol is found. Objetos from this region often date back billions of years before solar formation.
The composition rich in heavy elements reinforces the hypothesis of primordial origin. Diferenciações chemistries indicate that the comet preserved material from times before most of today’s stars.
Comparisons with galactic evolutionary models support the possibility of an age greater than 10 billion years. Essa characteristic positions 3I/ATLAS as a potential relic of the early universe.
Comparison with other interstellar visitors
3I/ATLAS is the third confirmed interstellar object, after 1I/’Oumuamua in 2017 and 2I/Borisov in 2019. Diferente from the asteroid-like ‘Oumuamua, it displays clear cometary activity, with a coma and tail.
- Volatile activity: Presença of jets and gaseous emissions, absent in ‘Oumuamua.
- Composition: Maior richness in carbon dioxide than Borisov.
- Trajectory: Excentricidade orbital greater than 1, confirming external origin.
- Speed: Excesso in relation to the local solar system, similar to its predecessors.
Borisov had a long tail and a composition closer to solar comets. Já 3I/ATLAS stands out for its primitive chemistry and potentially greater age.
‘Oumuamua has sparked debates about non-gravitational acceleration. 3I/ATLAS follows natural cometary patterns, with no significant anomalies detected so far.
Terrestrial and space observations
Ground-based telescopes at Hemisfério Sul captured the first images after the ATLAS discovery. The system, operational since 2022 on Chile, identified the object as an interstellar candidate.
Telescópio Gemini North produced color images in December 2025, revealing a greenish glow. Essas captures occurred after the comet emerged from behind Sol on its outbound trajectory.
The Europa Clipper mission performed opportunistic observations in November 2025. Instrumentos onboard recorded supplementary data while the comet was visible from the probe’s position.
The XMM-Newton observatory dedicated 20 hours of observation on December 3, 2025. Registros in X-rays helped map interactions with the solar wind.
Implications for astronomy
The 3I/ATLAS flyby offers unique window into the chemistry of distant stellar systems. Dados collected allow you to compare planetary formations in different galactic epochs.
Studies of the object’s dynamics refine models of interstellar distribution. Estimativas indicate thousands of similar ones in Via Láctea.
The high age suggests preservation of primordial material. Análises spectroscopy reveals physical processes from billions of years ago.
Searches continue as the comet moves away. Telescópios maintain monitoring to capture final variations in activity.
3I/ATLAS consolidates the category of interstellar visitors. Descobertas future ones depend on surveys like ATLAS and the future LSST.
Technical details of the discovery
Initial identification occurred on July 1, 2025 as object A11pl3Z. Fast Análises confirmed high orbital eccentricity, leading to the provisional designation C/2025 N1.
International teams coordinated follow-up observations. Mais of 30 telescopes participated in the first few weeks.
Entry speed exceeded 60 km/s relative to Sol. Esse value indicates ejection from ancient star system.
Models predict permanent exit from the solar system in the coming years. The object will not return.
Observed characteristics
- Rotation period: approximately 15.5 hours.
- Perihelion distance: 1.4 AU in October 2025.
- Approximation Terra: December 19, 2025.
- Dominant composition: carbon dioxide, nickel and iron.
- Structures: coma, tail and oscillating jets.
These features distinguish 3I/ATLAS from typical solar comets. Continuous Observações refined orbital parameters.
