The arrival of comet 3I/ATLAS has turned the agendas of astronomers and space agencies upside down: it's not every day that a visitor from outside the Solar System sneaks into our neighborhood. This object, detected by the ATLAS system, has become a centerpiece due to its rarity and the scientific interest it arouses.
We are talking about a traveler who comes from another system and is speeding through the planetary region, on a trajectory that betrays its interstellar origin. Here we tell you what it is, where it is, when it will appear so we can see it, and what the probes closely following it are discovering.
What is 3I/ATLAS and why is it special?
3I/ATLAS is a comet identified by the ATLAS program in Chile, and his surname reveals the discovery. The designation 3I indicates that he is the third interstellar visitor confirmed after 1I/ʻOumuamua and 2I/Borisov, a category reserved for objects that are not gravitationally bound to the Sun.
His trajectory is unequivocal: he follows a hyperbolic orbit, which means it will only pass through the solar vicinity once before disappearing back into deep space. It travels at over 200.000 km/h, a speed typical for this type of interloper, and has already developed a coma and a dust tail which allow us to study it in detail.
In addition to its dynamism, its behavior has been unusual from afar: it showed activity when it was still beyond Jupiter, a trait that suggests very volatile ice and provides clues about the environment in which it was formed.
Key dates: when and how it can be observed
The comet will reach its closest point to the Sun around October 30, a time when visibility from Earth is not guaranteed due to its position relative to the star. However, as November progresses, and especially in December, it could once again be within range. amateur instrumentation.
Anyone who wants to try to catch it will have to arm themselves with patience and a good-diameter telescope, since it is not expected to exceed magnitude 12. In other words: will not be visible to the naked eye and it will take dark skies, up-to-date maps, and stable conditions to distinguish its faint glow.
- Perihelion: late October, with the comet on the other side of the Sun from our perspective.
- Best window from the ground: when it reappears in late November and during December, with medium telescopes.
- Expected brightness: magnitude 12 environment; essential adequate optics.
Where is it now and what are the Mars probes seeing?
At this moment, 3I/ATLAS is moving through the Martian region, in a geometry that places it after the sun's glare for Earth-based observers. This same configuration has given Mars-bound spacecraft an advantage, taking over with cameras and spectrometers.
Between 1 and 7 October, several missions – Mars Express and ExoMars TGO (ESA), MRO and MAVEN (NASA), the Hope probe (UAE) and Tianwen-1 (China) – have targeted a target that passed within a few 29-30 million kilometers of the red planet. The first ExoMars sequences, with five-second exposures, managed to separate the comet from the stellar background and record its relative motion.
These observations, although challenging for instruments designed for Mars, serve to measure the size of the coma, follow the evolution of the tail and compare the real brightness with the orbital predictionsThe teams hope to extract information about dust grain size and gas distribution from red, blue, and near-infrared filters.
The European agency and collaborators confirm that, for now, the comet is behaving as expected in position and luminosity, which facilitates coordination with other observatories and the chaining of data between missions.
Trajectory and safety: a close but safe step
Dynamical calculations show a highly inclined and open orbit, with a passage through the solar interior that poses no risk to our planet. The object will not approach closer than just over 1,8 AU from Earth (about 270 million km), so any impact scenario is ruled out.
After the perihelion in late October, the comet will continue to move away, with a crossing of Jupiter's orbit expected in early 2026. In that stretch, missions such as JUICE (ESA) They have planned observations between early and mid-November to monitor the evolution of its coma and tail when activity is at its peak.
In the environment of Mars, the shorter distance of passage—about 0,195 AU—has been a perfect opportunity to study its structure without direct interference from the Sun. sunshineFrom there, the visitor will continue their exit route and, over time, fade away into the starry background.
In short: it is a meeting unrepeatable with an object that will never return. It's a short, intense, and scientifically very valuable visit to reconstruct its history of expulsion from another star system.
What its composition tells us about its origin
Initial spectroscopic analyses point to a mixture rich in water ice and carbon dioxide, with weaker carbon monoxide signals than usual. This combination suggests that 3I/ATLAS may have formed in cold regions of a protoplanetary disk with abundant CO₂ or experienced warming episodes that reduced CO₂.
Space telescopes like Hubble and JWST, along with dedicated infrared mapping missions, are measuring the gas balance and dust size in the coma. With this data, teams hope to outline the chemical footprint of the comet and compare it with that of the “domestic” comets of our Solar System.
If this carbon-rich chemistry is confirmed, the object will provide clues about how molecules are assembled. planetesimals around other stars and what mechanisms can expel them into interstellar space to end up, from time to time, crossing into our neighborhood.
Rumors, clarifications and what's next
As is often the case with such striking phenomena, exaggerated claims have circulated on social media: from alleged risks of impact to artificial originsSpace agencies have been adamant: 3I/ATLAS poses no danger and is, above all, a unique opportunity for science.
In the coming weeks a coordinated campaign between planetary missions and telescopes to put all the pieces together: brightness, activity, dynamics, and composition. In the meantime, amateurs can prepare celestial charts and equipment because, weather permitting, December will offer the best option to try to capture it from Earth with a telescope.
A comet from another world, a fleet of ships following it, and a demanding observation window: this is how 3I/ATLAS, a visitor, presents itself. fleeting and unrepeatable which will leave an extraordinary harvest of data before heading back to interstellar space.
