A sequence of images compiled by the TESS satellite of Nasa resulted in a 28-hour video documenting the passage of the interstellar comet 3I/ATLAS through space. The observations, carried out in January, show the object as a bright point with a prominent tail, moving against a background of distant stars. Este record offers an extended and rare look at a celestial body originating from another star system.
The material was captured between January 15th and 22nd, 2026, a period in which the comet was already moving away from Sol after reaching the closest point in its orbit, known as perihelion. The compilation of images was coordinated by Daniel Muthukrishna, a researcher at Instituto of Tecnologia of Massachusetts (MIT) who is part of the TESS mission scientific team. The result is a valuable visual document about the object’s dynamics and behavior.
The 3I/ATLAS capture demonstrates the versatility of the satellite, whose main mission is to detect planets outside our Sistema Solar. The ability to record a fast-moving object like this comet expands the technology’s scope of application, providing crucial data for planetary astronomy and the study of interstellar visitors, which remain events of great rarity and scientific interest.
The unexpected capabilities of TESS
Designed to monitor large areas of the sky for long periods, Transiting Exoplanet Survey Satellite (TESS) looks for small dips in the brightness of stars, an indication of the passage of an exoplanet. However, its wide field of view proved ideal for following the trajectory of 3I/ATLAS. Análises later revealed that the satellite had already recorded the object in May 2025, almost two months before its official discovery, although at the time it appeared without the cometary activity visible later.
Assembling the video faced a slight technical challenge, as a failure in TESS’s solar panels forced the satellite into safe mode, interrupting observations between January 15th and 18th. Apesar of the break, the number of images collected in the following days was sufficient to clearly reconstruct the comet’s path, allowing scientists to analyze its movement and brightness variations continuously during the recorded period.
Analysis of the comet’s tail and rotation
The video compiled from the TESS data clearly displays the comet’s antisolar tail, a structure of dust and gas that points in the opposite direction to its position relative to Sol. Esse phenomenon is characteristic of active comets, in which solar heat sublimates surface ices, releasing material. Embora the angular resolution of TESS does not allow us to visualize fine details, the long observation sequence is essential for studying fluctuations in the object’s brightness. The researchers plan to use these variations to confirm the rotation period of the comet’s nucleus, previously estimated to be about 7.1 hours based on images of Telescópio Espacial Hubble. Spectroscopic analysis also indicated that the comet releases relatively large dust grains and has a reddish color, similar to type D asteroids, suggesting a composition rich in irradiated organic compounds. 3I/ATLAS activity intensified significantly after its passage through perihelion, making the January observations particularly revealing.
The journey of an object from another star system
Comet 3I/ATLAS was officially discovered on July 1, 2025 through the Asteroid Terrestrial-impact Last Alert System (ATLAS) system, located at Chile.
A few days after its detection, analysis of its trajectory confirmed its interstellar origin. The comet follows a sharp hyperbolic orbit, which means its speed is too high for it to be captured by Sol’s gravity.
The object reached its perihelion on October 30, 2025, passing about 1.4 astronomical units from Sol, a distance slightly greater than Terra’s orbit, before beginning its journey back into interstellar space.
Differences between interstellar visitors
3I/ATLAS is the third interstellar object confirmed to cross our Sistema Solar, and each has displayed distinct characteristics that intrigue scientists.
The first, 1I/’Oumuamua, detected in 2017, drew attention due to its extremely elongated shape and the absence of a visible coma, which made it an object difficult to classify.
The second, 2I/Borisov, identified in 2019, exhibited behavior more typical of a comet, with a well-defined tail of dust and gas, similar to the comets of our own Sistema Solar.
3I/ATLAS, in turn, developed an evident coma and tail from great distances, providing more material for analyzing its composition and dynamic behavior.
A multi-satellite observation campaign
The 3I/ATLAS study was not limited to TESS, involving a collaboration between several Nasa space missions to obtain the most complete picture of the visitor possible.
Telescópio Espacial Hubble captured 36 very high-resolution images of the comet between November 2025 and January 2026, taking advantage of a rare alignment between the object, Terra and Sol.
These detailed images of Hubble are crucial for revealing fine structures in the tail and possible jets of material emanating from the core, serving as a reference for calibrating analyzes of TESS’ lower-resolution video.
The observation campaign will continue in March 2026, when the Juno probe, currently in orbit around Júpiter, will have the opportunity to observe the comet from a distance of approximately 53.6 million kilometers, using its various instruments to collect additional data.
Implications for astrophysics
The study of objects such as 3I/ATLAS is fundamental for astrophysics, as they function as direct probes of other planetary systems. Analysis of its chemical composition, the proportion of elements and the behavior of its volatile ices offers valuable clues about the conditions and materials present in its region of origin, allowing scientists to compare the formation of stellar systems in different parts of the galaxy.
Open data and scientific collaboration
Following Nasa’s transparency policy, all raw data collected by TESS is publicly available on Arquivo Mikulski for Telescópios Espaciais (MAST).
This availability allows researchers from around the world, as well as amateur astronomers, to analyze the images independently, contributing to new discoveries about 3I/ATLAS. The comet’s passage has been monitored by a global network of ground-based telescopes, which complement space data and ensure continuous monitoring while the object remains within instrument range.
