A cosmic object originating from another star system, the interstellar comet 3I/ATLAS, began to exhibit unmistakable signs of fragmentation during its approach to Sol. The phenomenon, closely observed by space agencies around the world, had its first signs recorded at the end of October 2025, when the star reached its perihelion, the closest point in its orbit around our star.
The disintegration is driven by intense solar radiation, which heats the comet’s surface and causes the sublimation of its volatile ices. Este process releases jets of gas and dust into space, creating a temporary atmosphere known as a coma and, at the same time, exerting forces that destabilize the fragile structure of its core, estimated to be less than a kilometer in diameter.
The scientific community follows each stage of the event, using a global network of space and ground-based telescopes. Analysis of the fragments and ejecta offers an unprecedented opportunity to study the composition of a body formed in a planetary system distinct from our own, providing valuable clues about the formation of planets and comets elsewhere in the galaxy.
A unique trajectory through the solar system
Discovered in July 2025 by the ATLAS telescope system (Asteroid Terrestrial-impact Last Alert System) on Havaí, 3I/ATLAS was quickly identified as an interstellar visitor due to its hyperbolic trajectory. Diferente of our Sistema Solar’s comets, which follow elliptical orbits and return periodically, a hyperbolic orbit indicates that the object has sufficient speed to escape the gravitational pull of Sol. Essa feature confirms that its origin lies far beyond the borders of our planetary system, having traveled for millions, perhaps billions of years, through the interstellar vacuum.
Its speed, which exceeds 60 kilometers per second, is a testimony to its long journey. Astrônomos calculate that the comet was probably ejected from its home star system due to a strong gravitational interaction, perhaps with a giant planet or massive star. Desde its detection near the orbit of Júpiter, its trajectory was accurately monitored to predict its behavior as it approached Sol. The passage through perihelion, at a distance of 1.4 astronomical units (about 210 million kilometers) from Sol, marked the period of maximum activity and, consequently, the beginning of its structural disintegration.
Chemical composition reveals distant origins
Spectroscopic analysis of the gas and dust released by 3I/ATLAS revealed a fascinating and distinct chemical composition that sets it apart from native Sistema Solar comets. The Hubble and James Webb space telescopes were instrumental in identifying the presence of rare organic molecules, as well as compounds such as carbon dioxide, hydrocyanic acid and, notably, nickel vapors. The detection of nickel in a gaseous state suggests that the comet formed in an extremely cold region, far from its parent star, where stellar radiation was weak. Sua composition rich in volatile materials points to an origin in a cold molecular cloud, a nursery of stars and planets. Comparison with data from previous interstellar visitors, 1I/’Oumuamua and 2I/Borisov, allows scientists to build a more complete picture of the chemical diversity of planetary building blocks in other star systems. Cada identified compound functions like a chemical fossil, preserving information about the conditions and processes that governed its birth environment.
Signs of disintegration under solar heat
The approach of Sol acted as a trigger for the destabilization of the comet’s nucleus. Intense solar radiation heated its surface, causing water ice, carbon dioxide and other volatile substances to pass directly from a solid to a gaseous state.
This sublimation process does not occur uniformly. The pressure of gas accumulated under the surface crust can lead to sudden explosions, which eject large amounts of material and create fissures in the structure of the nucleus, as observed in similar events on comet 2I/Borisov.
Astronomers observed a significant increase in the comet’s brightness, followed by the formation of an elongated, asymmetrical coma that stretched for thousands of kilometers.
These are classic signs that the nucleus is fragmenting into smaller pieces, a process that can lead to its complete disintegration in a matter of hours or days.
Global observers monitor the phenomenon
An internationally coordinated observation campaign was mobilized to study 3I/ATLAS. Cutting-edge Telescópios on Chile and Havaí provided daily data on changes in their brightness and structure, allowing rapid response to any sudden changes in their activity.
Telescópio Espacial Hubble captured high-resolution images that revealed the shape of the dust cloud and the possible ejection of larger fragments. Simultaneamente, Telescópio Espacial James Webb used its infrared instruments to analyze the thermal and chemical composition of the released material.
Missions in orbit around Marte, such as Trace Gas Orbiter from Agência Espacial Europeia (ESA), also contributed observations from a different point of view, recording images of the comet from a distance of approximately 30 million kilometers.
What differentiates 3I/ATLAS from other comets
One of the most intriguing features of 3I/ATLAS was the behavior of its dust plume. Diferente of traditional dust tails, which are pushed by solar radiation pressure and point in the opposite direction to Sol, the main dust emission from 3I/ATLAS appeared directed toward Sol.
This unusual phenomenon suggests that the ejected particles were large enough not to be immediately affected by radiation pressure, following a trajectory more influenced by the comet’s original orbit. Essa dynamics, along with its volatile-rich chemical composition, reinforces the idea that the comet formed in an environment very different from our Cinturão of Kuiper or the Nuvem of Oort.
Real-time spectral analysis
Collaboration between NASA and ESA was essential to process the volume of data generated. The agencies worked together on real-time spectral analysis, allowing rapid identification of the chemical “fingerprints” of the elements and molecules present in the comet’s coma.
Solar-observing satellites such as GOES-19 were also used to capture fluctuations during the comet’s solar conjunction on October 21, when it passed behind Sol from our observation point. Agências spacecraft from other countries, such as Austrália, contributed to studies on sublimation, correlating brightness data with the rate of gas and dust release.
Predictions for the comet’s future
As 3I/ATLAS began to move away from Sol from November 2025, models predicted progressive visual weakening. Caso did not disintegrate completely, scientists estimate that the comet could lose up to 20% of its total mass during this single pass by our Sistema Solar. Sua’s minimum distance from Terra was 270 million kilometers, without posing any risk of collision, with the main objective remaining data collection as the object continues its journey back to interstellar space.