Less than a decade ago, the idea of detecting an object of another solar system through our neighborhood was science fiction material. Astronomers were clear that they existed, but believed that our chances of detecting them were practically null due to the limitations of current technology. In 2017, everything changed.
First appeared 1i/ʻoumuamua. An object that baffled astronomers. Not only because it was the first interstellar object discovered in our solar system, but because its nature was and remains a mystery. With a strange form, as elongated as a cigar or flat as an album, and a size of just 100 or 200 meters, it happened fleetingly leaving more questions than answers. Was it a comet, an asteroid or something completely new? The debate continues while moving away from us.
Then 2i/Borisov was discovered. When we still wondered if we would see something similar in our lives, the answer came alone. In 2019, astronomers detected a second object of another star system that was unequivocally a kite, somewhat larger than its predecessor (about 400-500 meters) and with a very different trajectory. Borisov confirmed that ‘Oumuamua had not been an anomaly. Interstellar visitors were real and we are able to find them.
And to confirm it, 3I/Atlas arrives. On July 1, 2025, the Telescopes of the Atlas Network in Chile detected the third known interstellar object. After confirming his hyperbolic trajectory, he was officially baptized as 3i/Atlas. It is a real giant compared to the previous two, and marks a before and after in the study of these bodies.
Like Borisov, it shows a clear comment activity, with a comma and a tail that lengthens as it approaches the sun. Therefore, it is a kite. But it is much bigger. Although the measurements are refining, initial estimates place their diameter between 5 and 20 kilometers. A colossal size that makes it much easier to study.
A giant who will pass through Mars. 3i/Atlas is incredibly fast. It moves at an exhaust speed of about 58-60 km/s with respect to the Sun. much faster than ‘oumuamua (26 km/s) and Borisov (32 km/s). His career is also unique. It will reach its closest point to the Sun (its perihelium) on October 29, passing between the orbits of Mars and the Earth.
Although at that time our planet will be on the other side of the sun, which will prevent its direct observation, it will be only 31.4 million kilometers from Mars on October 3. This opens a fascinating opportunity: that some of the probes that orbit the red planet, such as the Mars Reconnaissance Orbiter, can capture images of the interstellar traveler.
Three important findings. Each of these objects is a time capsule from another solar system. All planets, asteroids and comets of our system share a common origin, but these visitors are authentic outsiders. They contain clues about the formation and composition of worlds that orbit other stars. Studying them is like receiving a geological sample from a corner of the galaxy that would take millennia to visit.
Until now, we could only observe his fleeting step. But this is about to change. ESA is already preparing the Mission Interceptor, whose launch is scheduled for 2029. The idea is ingenious: the probe will not have a predefined objective, but will “park” at a point in Lagrange (L2) waiting for a pristine kite of a long period or, with some lucky, a new interstellar visitor to be within reach.
It would be the first rapid response mission to intercept one of these mysterious objects. In less than ten years we have not known if they existed to actively plan how to send a ship to touch them. With new generation observatories such as Vera Rubin, which is expected to find dozens of them in the next decade, we are entering a new era of astronomy. The universe sometimes brings us its secrets at home.
Image | The interstellar comet 3i/Atlas (ESA)
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