They weren’t just lost comets. Interstellar objects like 3I/ATLAS could have seeded planets around other stars.
Every now and then, the cosmos reminds us that its rules are not as rigid as we believe. Objects like ʻOumuamua, Borisov, or the most recent one have reopened an old debate about planet formation. Now, a group of scientists suggests that these visitors are not just wanderers: they could be the initial spark that allows for the birth of new planets.
### Interstellar Objects as Cosmic Seeds
In a conference held in Helsinki, astrophysicist Susanne Pfalzner presented simulations that reconsider the role of foreign comets and asteroids. According to her models, these bodies can get trapped in the gas and dust disks surrounding newly born stars. Once there, they act as solid cores that accumulate material and, within thousands of years, turn into planetesimals. This process could explain something that puzzles traditional theory: in the usual models, small solid particles in a disk tend to break apart or bounce off, making it difficult for larger bodies to form. This changes the rules, acting as a natural catalyst in the process.
### 3I/ATLAS and the Evidence Challenging the Known
3I/ATLAS, discovered in 2025, shows chemical signals that do not match those of the solar system. Even its cometary activity — the release of gases at great distances from the Sun — points to a different composition, shaped by another stellar environment.
According to Pfalzner, if massive disks around young stars capture millions of these objects, the formation of giant planets could be accelerated surprisingly. And this aligns with what is already observed.
### The Invisible Exchange Between Stars
The three confirmed interstellar objects so far demonstrate that the exchange of matter between stellar systems is much more common than imagined. Each of them could be a “cosmic letter” sent from a different corner of the galaxy.
The challenge now is to quantify the real impact of this process. What percentage of planets were born thanks to these wandering seeds? In which regions of the protoplanetary disk is it more likely to occur? Open questions that new simulations and telescopes will seek to answer.
It is not just a fleeting visitor. It represents the possibility that the planets we now consider as consolidated worlds may have received the initial push from an interstellar traveler in their early days. The universe seems to share seeds, and each young star could be a laboratory where borrowed matter from other suns flourishes.
