We know of three interstellar objects (ISO) that have visited our inner solar system. Oumuamua was the first one, and it came and went in 2017. 2l/Borisov, an interstellar comet, was next, appearing in 2019. And right now, the interstellar comet 3I/Atlas is enjoying a visit to the sun-warmed inner solar system.
We know of three interstellar objects (ISO) that have visited our inner solar system. Oumuamua was the first one, and it came and went in 2017. 2l/Borisov, an interstellar comet, was next, appearing in 2019. And right now, the interstellar comet 3I/Atlas is enjoying a visit to the sun-warmed inner solar system.
A massive number of ISOs must have passed through our solar system during its long, 4.6 billion year history. It’s possible that some of them slammed into Earth. Maybe ISOs are responsible for some of the ancient impact craters whose remnants we can still see today, like the Vredefort impact structure.
Our solar system is much more placid than it used to be. Early in its history, it was molded by chaotic collisions. There are fewer rocks and fewer collisions now because much of the rock accreted into the terrestrial planets. But the same can’t be said about ISOs. There’s no reason to believe there are fewer ISOs entering our solar system than there were in the past.
That means they pose an impact risk to Earth. Is there any way to quantify that risk?
New research titled «The Distribution of Earth-Impacting Interstellar Objects» tries to understand the risk. The lead author is Darryl Seligman, an assistant professor in the Physics and Astronomy Department at Michigan State University. The study is published on the arXiv preprint server.
«In this paper we calculate the expected orbital elements, radiants, and velocities of Earth-impacting interstellar objects», the authors write. Their work doesn’t calculate the number of ISOs because there are no constraints on the number to work with. Their work only concerns their expected distribution.
When it comes to the source of ISOs, they focus on what are called M-star kinematics. M-stars, also known as red dwarfs, are the most numerous type of star in the Milky Way. It stands to reason that most ISOs would be ejected from M-dwarf solar systems purely based on numbers. However, the authors admit this is somewhat arbitrary. «This choice is admittedly somewhat arbitrary because the kinematics of interstellar objects is unconstrained», they explain.
