As of 2017, we know for sure that interstellar objects are appearing in the Solar System. These are visitors who enter the Solar System from interstellar space and leave it again after some time. In 2017, we discovered the object 1i / Oumi’stwo years later an interstellar comet 2I/Borisov and another interstellar comet a few months ago 3I/ATLAS.
All indications are that such interstellar objects are not uncommon. Quite the opposite. During its 4.6 billion years of history, the Solar System has had to encounter an enormous number of these objects. It is quite possible that some of them have crashed into planets, including our Earth, and are responsible for some of the craters we have found on Earth and other planets.
An interstellar threat
The solar system is much calmer today than it used to be. Planets at its dawn and early stage used to be bombarded by a large number of bodies. Now there is less solid material in it, and therefore collisions occur less often, also because a large part of the original material has become part of the planets. However, this is definitely not true of interstellar objects. Other planetary systems are forming and disappearing around us, and there is no reason to think that there are significantly fewer interstellar objects now than before.
So it’s obviously a risk, an unpleasant one at that, because interstellar objects are more difficult to detect than objects that are constantly orbiting the Sun. Darryl Seligman from Michigan State University and his colleagues tried to find out more about the risk of interstellar objects to Earth.
The goal of a so far unreviewed study by Seligman’s team, published on the server arXiv, was not to find out how many interstellar objects there might be, but where they come from and how they behave.
According to the findings of the scientists, most interstellar objects have “red dwarf kinematics”. Seligman therefore assumes that most of them come from the vicinity of red dwarfs, the most common stars in the Milky Way.
Risk? Unknown!
The simulations also showed that fast objects can enter the Solar System more often, but slower objects pose a greater risk to Earth. The reason, according to scientists, is the fact that the Sun can more effectively gravitationally capture slower hyperbolic objects, which can then be deflected into orbits that intersect the Earth’s trajectory.
Seligman’s team also identified a surprising seasonal effect: in the spring (from the Northern Hemisphere perspective) according to scientists, the fastest and less dangerous interstellar objects arrive in the Solar System, on the contrary, there are fewer of them in the winter months, but they are slower and thus pose a higher risk to Earth. According to Seligman, the difference is due to the different setting of the Earth’s position.
The riskiest areas on Earth in terms of possible collisions are the areas around the equator. Simulations show that low latitudes are most prone to impacts from interstellar objects. More dangerous in terms of possible damage are the impacts on the northern hemisphere, where the majority of the global population lives.
Scientists still have no idea (due to the lack of data) how big a threat interstellar objects actually pose. It could provide answers to these questions Vera Rubin Observatorywhich could reveal tens to hundreds of interstellar visitors.
