Interstellar objects may seed planet formation around stars.
New research suggests that interstellar objects—like the ones we’ve seen passing through our solar system—might play a surprising role in helping planets form around young stars.
This idea could help solve a stubborn puzzle in astronomy: how small particles of dust grow into full-sized planets without breaking apart along the way.
Solving the Accretion Problem
Astronomers have long been puzzled by what’s called the “meter-sized barrier.” In the swirling disks of gas and dust around young stars, particles tend to grow easily up to about a meter in size.
But after that, things get tricky. When these boulders collide, they’re more likely to bounce off each other or shatter than to stick together and grow. That makes it hard to explain how planets ever get started.
Professor Susanne Pfalzner, from Forschungszentrum Jülich in Germany, shared new computer simulations this week showing that interstellar objects—like ‘Oumuamua or the recently discovered 3I/ATLAS—could act as “cosmic seeds.”
If a young star’s disk captures even a few of these visitors, which are already tens or hundreds of meters in size, they could jump-start planet formation. Instead of slowly building from dust, new planets could form around these ready-made cores.
Explaining Giant Planet Distribution
This might also explain why gas giant planets, like Jupiter, are much more common around Sun-like stars than around smaller, dimmer stars called M dwarfs.
Larger stars have stronger gravity and bigger disks, making it easier for them to catch these interstellar passers-by. That could give them a head start in forming planets quickly—before their gas disks fade away.
Interstellar Object Context
We’ve only known about interstellar objects since 2017, when ‘Oumuamua flew through our solar system. Since then, two more have been spotted, including 3I/ATLAS, which is expected to make its closest approach to the Sun this October.
Early observations suggest it’s rich in carbon dioxide and could be incredibly old—possibly over 7 billion years.
Pfalzner plans to continue modeling how often these objects get captured, and where they end up in planet-forming disks.
It’s a promising idea—one that might finally help us understand how planets take shape in the chaotic early stages of a star’s life.
