Unusual orbits and colors of objects at the edge of the Solar System may indicate the close passage of another star. This conclusion was reached by the authors of a study published on the arXiv preprint server.
Icy relics at the edge of the Solar System
Trans-Neptunian objects (TNOs) are among the least known bodies in our Solar System. There are thousands of them, and their name comes from their orbits, which are farther away than Neptune. The most famous representative of this group is Pluto.
Essentially, TNOs are relics of the early Solar System. They formed in cold, remote regions of the protoplanetary disk. At that time, the young Solar System was more chaotic and dynamic, and as the giant planets migrated, gravitational interactions formed the orbits along which the TNOs moved.
As a result, many of them follow eccentric orbits that are slightly tilted relative to the plane of the planets. They make up what is known as the scattered disk. TNOs also have another unusual feature: a complex distribution of colors ranging from gray to red. Astronomers believe that this is due to the different types of ice and complex chemicals on their surface. One such chemical substance is tholins, which give Pluto its reddish hue.
It is noteworthy that the distribution of colors is not random and implies a correlation with their orbits. Thus, the color of the TNO indicates the part of the protoplanetary disk in which it formed and its subsequent dynamic interactions with other bodies.
Close encounter with a star
A new study, which will be published in The Astrophysical Journal Letters, suggests that the unusual orbits and current color distribution of TNOs are the result of a close flyby of another star. Scientists came to this conclusion as a result of modeling performed on a supercomputer. They modeled a star with a mass of 0.8 solar masses flying at a distance of up to 150 AU.
The study showed that the star’s passage led to significant perturbations of the orbits of TNOs and the formation of groups similar to those that actually exist, with the exception of populations that were generated later as a result of interactions with Neptune. Researchers conducted a simulation covering one billion years. It showed that the star’s influence became insignificant 12,000 years after the close encounter, after which the overall structure of the TNO did not change significantly.
According to scientists, if the flyby did occur, it probably happened at the earliest stage of the Solar System’s history, when it was part of a star cluster. In such clusters, the density of stars is approximately 1,000 to 1,000,000 times higher than it is now in the vicinity of the Sun, and therefore close flybys were much more common.
Scientists hope that the results of observations from the recently commissioned Vera Rubin Observatory will help verify the accuracy of their modeling. If they are correct, then the distant TNOs will predominantly have light red and gray hues, while there will be noticeably fewer bright red objects.
According to Phys.org
