Interstellar comet 3I/ATLAS has an eruption observed by NASA’s Spherex telescope as it exits the system

The Spherex space telescope captured infrared images of the interstellar comet 3I/ATLAS in December 2025. The object showed intense activity, with the release of gas, dust and complex molecules, two months after its closest approach to Sol.

Observations revealed a glowing coma rich in water vapor, carbon dioxide and organic compounds. A pear-shaped dust tail was also identified, resulting from the ejection of rocky material.

The phenomenon occurred as the comet moved away from the inner solar system. The unexpected activity provided detailed data on the chemical composition of an object formed in another star system.

• Comet 3I/ATLAS was discovered on July 1, 2025 by the ATLAS program.
• This is the third confirmed interstellar object to pass through the solar system.
• Its hyperbolic trajectory indicates origin outside our system.

Discovery and trajectory of the object

The ATLAS program identified comet 3I/ATLAS in July 2025 at Chile. The hyperbolic orbit quickly confirmed its interstellar origin, differentiating it from solar system comets.

The object reached perihelion on October 30, 2025, at about 1.4 astronomical units from Sol. Após this passage, a gradual reduction in activity was expected, but the behavior was different.

Activity observed in December

Spherex carried out observations in December 2025, when the comet was already moving towards the outer solar system. The instrument recorded a significant increase in brightness, caused by sublimation of deep ice.

The developed coma contained water vapor sublimating even at distances greater than Sol. The phenomenon indicated slow penetration of solar heat into the inner layers of the core.

Chemical composition detected

Infrared images revealed the presence of carbon dioxide in large quantities. Esse compound, together with water vapor, formed the basis of the recorded activity.

Complex organic molecules have also been identified in coma. Essas substances include basic ingredients for planet formation in other star systems.

The instrument also detected traces of methane and methanol. Esses components reinforce the chemical diversity of interstellar material.

The dust tail had a characteristic pear shape. The configuration results from the continuous ejection of rock particles during the eruption.

Spherex telescope capabilities

The Spherex operates exclusively in the infrared range, allowing precise identification of ices and molecules. Essa characteristic makes it ideal for analyzing distant comets.

The mission was designed to map the universe at different wavelengths. The 3I/ATLAS observations demonstrated practical application in studies of transient objects.

Comparison with previous objects

Comet 3I/ATLAS differs from 1I/’Oumuamua, detected in 2017, which did not have a visible coma. The absence of activity in the first interstellar object limited detailed chemical analyses.

2I/Borisov, identified in 2019, showed a coma and tail similar to solar comets. However, the late 3I/ATLAS eruption offers unique data on delayed sublimation.

The third visitor shows greater brightness and prolonged activity. Essas features facilitate direct comparisons with material formed in distinct stellar environments.

The trajectory of 3I/ATLAS maintains a high speed, exceeding 30 kilometers per second. Esse value confirms its external origin and prevents gravitational capture by Sol.

Molecules identified in coma

The Spherex observations listed several components in the cloud surrounding the nucleus. The simultaneous presence indicates preservation of primordial material.

• Water vapor in active sublimation
• Dominant carbon dioxide
• Methane detected in traces
• Methanol present in measurable quantities
• Various complex organic compounds
• Cyanide at low levels

Importance of the data collected

The recorded eruption provides clear insight into the chemistry of objects formed outside the solar system. The detected components correspond to building blocks of planetary systems.

Late activity reveals internal thermal processes different from local comets. Solar heat reached buried ice months after perihelion.

Data from Spherex complement observations from other instruments on Nasa. The combination allows for a complete reconstruction of the comet’s evolution during its passage.

Analysis of ejected dust provides information about nucleus size and density. Estimativas initials indicate a diameter between 440 meters and 5.6 kilometers.

Context of interstellar objects

Interstellar objects represent material ejected from other stellar systems. Sua passage through the solar system offers a rare opportunity for direct study.

The confirmation of 3I/ATLAS as the third visitor reinforces estimates of the density of these bodies in the galaxy. Bilhões can cross the space close to Sol regularly.

Detection relies on monitoring programs like ATLAS. The system operates telescopes at Havaí and Chile for early identification of threats and unusual objects.

The high speed of the 3I/ATLAS prevents future return. The comet now heads towards the interstellar medium, carrying solar material on its surface.

Mission Details Spherex

Spherex was launched to study the history of the universe in infrared. Suas capabilities include wide range spectroscopy on transient objects.

The comet observation campaign took place in December 2025. The collected data is being processed for detailed spectral maps of the coma.

The mission remains active, with a calendar of observations of other targets. The success with 3I/ATLAS demonstrates the instrument’s operational flexibility.

The telescope maintains a stable position for extended captures. Essa stability was essential to record variations in the comet’s activity.

Current trajectory of the comet

3I/ATLAS now approaches the orbit of Júpiter on its exit. Increasing distance gradually reduces the remaining solar influence.

Ground-based observations complement the Spherex data at visible wavelengths. The combination allows a complete view of the tail structure.

The object maintains residual glow from the December eruption. The luminosity progressively decreases with distance.

The current speed exceeds the escape from the solar system. The comet is headed for deep interstellar space in the coming years.