Sun may have helped form “halo” of interstellar objects

Sun may have helped form "halo" of interstellar objects

The Solar System may be surrounded by a kind of “swarm” of interstellar objects, the name given to those coming from other star systems. That’s what concludes a new study by Jorge Peñarrubia, an astronomer at the University of Edinburgh, who has modeled how the gravity of the Sun and the Milky Way can affect these objects that approach our system.

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Our system does not exist in space as an isolated bubble – proof of this is the discovery of the interstellar object ‘Oumuamua. Identified in 2017, it has an elongated, rocky structure and was moving in a trajectory that suggested it came from somewhere in interstellar space. In 2019, it was the turn of the interstellar comet 2I/Borisov to be identified by astronomers.

In his study, Peñarrubia investigated the gravitational effects on these interstellar space rocks. He proposes that if one of them (like ‘Oumuamua) orbits the center of the Milky Way, it could eventually come close to the Solar System. Our galaxy’s gravity would slowly slow the asteroid down, allowing the Sun’s gravity to capture it and send it into a brief orbital dance.

We say it is brief because this visitor would not be in a stable orbit; in fact, it would complete a few orbits or part of one, and then be hurled back by the Sun into interstellar space—and with more energy than it had before the encounter. Thus, the object would be in a wider and faster orbit around the center of the Milky Way.

This process happens constantly, and this is where the conclusions of the Peñarrubia study come in: it proposes that if the Sun is all the time capturing new interstellar objects and “throwing” old ones, there is probably a constant number of them in a halo around it. of the Milky Way. These temporarily captured objects could form a sizable part of the Oort Cloud, a hypothetical cloud of frozen objects at the farthest reaches of the Solar System.

However, astronomers don’t know exactly how many of these intriguing objects might be part of the Solar System, let alone how many of them might exist in the cloud. “Even if these objects are out there, we still don’t have the technology to detect them in large numbers,” noted the author. But based on the few interstellar objects detected so far, he adds that the model predicts that there should be 10 million objects in the halo.

In fact, a few hundred of them may be orbiting our system as closely as Neptune does to the Sun. If Peñarrubia is correct, there could be a lot of these objects in the Solar System waiting to be studied. “If you manage to detect a sizable population of ‘trapped’ objects, we’ll have a lot of information about how many of them there are in the Milky Way and what the composition of the systems they come from is.”

The bad news is that the model says that even if these objects exist, they are so far away that even the James Webb Telescope would not be able to “see” them. On the other hand, there are different observation programs that can reveal them, and analyzes of their trajectory and movement can help in differentiating “local” objects.

The article with the results of the study was published in the journal Monthly Notices of the Royal Astronomical Society.

Source: Monthly Notices of the Royal Astronomical Society; Via: reverse