In our Solar System’s 4.6 billion-year history, three interstellar objects (ISOs) have visited us: Oumuamua in 2017, 2I/Borisov in 2019, and now 3I/Atlas. It’s likely many more have passed through, and some might have even collided with Earth.
Oumuamua was a mystery. It sped through the Solar System and raised questions about its origins. 2I/Borisov, on the other hand, was a comet that provided essential clues about other star systems. Now, 3I/Atlas is giving us another chance to learn.
Our Solar System is much quieter now than in its chaotic beginnings. Today, fewer rocks collide compared to earlier times. But the flow of ISOs hasn’t diminished. A recent study led by astrophysicist Darryl Seligman from Michigan State University explored the impact risk these objects pose to Earth. They focus on how ISOs might collide with our planet.
The research explored the expected paths (or “orbits”) of potential Earth-impacting ISOs. Seligman noted that their work doesn’t count how many ISOs there are—there’s simply no way to measure that yet. Instead, they looked at where these objects are likely to come from, focusing on a type of star called M-dwarfs, or red dwarfs. These stars are the most common in our galaxy, making it reasonable to assume ISOs primarily come from their systems.
The study found that ISOs tend to come from two main directions: one is from the solar apex, where our Sun moves through space, and the other is from the galactic plane, the flat region containing most stars. As the Solar System moves, it appears to “drive” through incoming ISOs, just like a car hitting more raindrops when driving through a storm.
Interestingly, ISOs arriving from the solar apex and galactic plane are likely to be moving quickly. However, those that could actually impact Earth tend to move slower. This is due to gravity’s influence, which can capture slower objects and send them on a collision course with us.
The timing of these potential impacts is also seasonal. Spring brings a higher chance of faster ISOs hitting Earth, while more objects might be on course in winter.
Low-latitude regions near the equator are at the most risk for impacts. Notably, areas in the Northern Hemisphere, where almost 90% of people live, also face higher chances.
This research is mainly focused on ISOs linked to M-dwarfs, but the findings could apply to other sources too. While the study doesn’t give a specific number of ISOs that may hit Earth, it helps lay groundwork for future observations. The Vera Rubin Observatory, set to observe the sky extensively, will enable astronomers to gather more data, either proving or challenging these findings.
As we explore our cosmic neighborhood, the study of ISOs is just beginning. It’s crucial for understanding our universe and assessing any potential risks. The topic is gaining attention online, with many discussions about what these objects could mean for Earth.
For further insights, you can read the study “The Distribution of Earth-Impacting Interstellar Objects” on arXiv.
