Computer Simulation Reveals Solution to a Cosmic Mystery
New findings suggest that billions of years ago, a star may have passed very close to our solar system. This event could have caused thousands of smaller celestial bodies in the outer solar system, beyond Neptune’s orbit, to be deflected into highly inclined orbits around the Sun. It is also possible that some of these bodies were captured as moons by the planets Jupiter and Saturn. These findings come from a team of astrophysicists at Forschungszentrum Jülich from Helmholtz Information and Leiden University in the Netherlands who uncovered these complex dynamics through modern computer simulations. They were published in two studies in the prestigious journals Nature Astronomy and Astrophysical Journal Letters. (Source: Forschungszentrum Jülich – Press Releases)
When we think about our solar system, we usually assume it ends at the outermost known planet, Neptune. “However, several thousand celestial bodies are known to move beyond Neptune’s orbit,” explains Susanne Pfalzner, an astrophysicist at Forschungszentrum Jülich. It is estimated that there are even tens of thousands of objects with diameters exceeding 100 kilometers. “Surprisingly, many of these so-called trans-Neptunian objects move in eccentric orbits that are inclined relative to the common orbital plane of the planets in the solar system.”
Copyright: NASA / JPL
Susanne Pfalzner, together with her colleague Amith Govind from Jülich and Simon Portegies Zwart from Leiden University, used more than 3,000 computer simulations to investigate a possible cause of the unusual orbits: Could another star have caused the strange trajectories of the trans-Neptunian objects?
The three astrophysicists found that a single, significant, close encounter with another star could explain the inclined and eccentric orbits of the known trans-Neptunian objects. “Even the orbits of very distant objects, such as the dwarf planet Sedna, discovered in 2003, at the farthest reaches of the solar system, can be explained this way. The same goes for objects that move in orbits almost perpendicular to the planets’ orbits,” says Susanne Pfalzner. Such a flyby can also explain the orbits of 2008 KV42 and 2011 KT19 — two celestial bodies that move in the opposite direction to the planets.
“The best match for the current outer solar system that we found in our simulations was a star slightly lighter than our Sun — about 0.8 solar masses,” explains Pfalzner’s colleague Amith Govind. “This star passed at a distance of about 16.5 billion kilometers from our Sun. That’s about 110 times the distance between the Earth and the Sun, just under four times the distance to the outermost planet, Neptune.”
The most surprising finding of the scientists, however, was that the flyby of a foreign star billions of years ago could also provide a natural explanation for more nearby phenomena. Susanne Pfalzner and her colleagues found that in their simulations, some trans-Neptunian objects were flung into our solar system—into the region of the outer giant planets, Jupiter, Saturn, Uranus, and Neptune.
“Some of these objects may have been captured as moons by the giant planets,” says Simon Portegies Zwart of Leiden University. “This would explain why the outer planets of our solar system have two different types of moons.” Unlike the regular moons, which orbit the planet in near-circular orbits, the irregular moons orbit the planet at a greater distance in inclined, elongated orbits. Until now, there has been no explanation for this phenomenon. “The beauty of this model lies in its simplicity,” Pfalzner adds. “It answers several open questions about our solar system with a single cause.”
Video: Simulation of a Stellar Flyby
The scientists at the Simulation and Data Lab for Astronomy and Astrophysics at Forschungszentrum Jülich conducted over 3,000 computer simulations to determine the cause of the unusual orbits of trans-Neptunian objects. The young Sun was surrounded by a disk of material from which the planets eventually formed. There is substantial evidence suggesting that the close flyby of another star could have disrupted this disk. The simulations demonstrate how such a close encounter would have significantly affected the orbits of the outer disk material. Many objects would have been ejected into eccentric orbits, far into space. While the outer solar system would have been completely restructured, the inner solar system, including Earth, would have remained unaffected.
FZJ/R. Panknin, 04.09.2024
Note: The article has been translated from German to English. It is based on a press release from FZJ.
The original press release can be found at:
Lösung für ein kosmisches Rätsel (only in german)
The original publication can be found at (Open Access):
“Trajectory of the Stellar Flyby Shaping the Outer Solar System” by Susanne Pfalzner, Amith Govind & Simon Portegies Zwart, Nature Astronomy (2024). DOI: 10.1038/s41550-024-02349-x
“Irregular moons possibly injected from the outer solar system by a stellar flyby“, Susanne Pfalzner, Amith Govind, and Frank W. Wagner, September 4 2024. The Astrophysical Journal Letters, Volume 972, Number 2. DOI: 10.3847/2041-8213/ad63a6
Localization in Helmholtz Information:
Helmholtz Information, Program 1: Engineering Digital Futures, Topic 1: Enabling Computational- & Data-intensive Science and Engineering
Contact:
Prof. Dr. Susanne Pfalzner
Institute for Advanced Simulation (IAS)
Jülich Supercomputing Centre (JSC)
Forschungszentrum Jülich
Phone: +49 2461 61-85420
E-Mail: s.pfalzner@fz-juelich.de
Amith Govind
Institute for Advanced Simulation (IAS)
Jülich Supercomputing Centre (JSC)
Forschungszentrum Jülich
Phone: +49 2461 61-9083
E-Mail: am.govind@fz-juelich.de
Contact for this press release:
Dr. Regine Panknin
Press Officer
Forschungszentrum Jülich
Phone: +49 2461 61-9054
E-Mail: r.panknin@fz-juelich.de
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