The many thousands of small celestial bodies beyond Neptune's orbit may have ended up there due to a star that passed close to the solar system billions of years ago. This is shown by Leiden simulation expert Simon Portegies Zwart, along with his German and Dutch colleagues. 'We are answering several open questions with one event.'
Astronomers have so far struggled to explain why there are thousands of celestial bodies with diameters over 100 kilometers orbiting the sun in elongated, tilted trajectories.
A team of researchers, including professor of Numerical star dynamics Simon Portegies Zwart has now conducted more than 3,000 computer simulations. These simulations suggest that a star, with roughly 0.8 times the mass of the sun, may have flown past billions of years ago. The star approached at an angle of about 70 degrees and at a distance around 110 times the Earth-sun distance. For comparison, Neptune is located at 30 times the Earth-sun distance.
Explanation for the orbits of various celestial bodies
The passing star not only explains the orbits of objects like the dwarf planet Sedna, but also those of objects moving almost perpendicular to the planetary orbits. It can also account for the orbits of 2008 KV42 and 2011 KT19, two celestial bodies orbiting in the opposite direction of the planets.
Explanation for different types of moons
'And, to our surprise, the simulations also provide an explanation for why Jupiter, Saturn, Uranus, and Neptune have two types of moons,' Simon Portegies Zwart adds. 'Due to the stellar flyby, some small celestial bodies from the outer regions were slung inward and captured by the giant planets. These became the irregular moons that orbit far away in tilted, elongated paths around the planets.'
'The beauty of the simulation and the resulting model lies in its simplicity,' says lead author Susanne Pfalzner of the Forschungszentrum Jülich in Germany. 'It answers several open questions with a single event.'
This post appeared as a press release on astronomy.com
Picture: Forschungszentrum Julich
Scientific articles
Trajectory of the stellar flyby that shaped the outer Solar System. Door: Susanne Pfalzner, Amith Govind & Simon Portegies Zwart. In: Nature Astronomy, 4 september 2024. [original (open access)]
Irregular moons possibly injected from the outer solar system by a stellar flyby. Door: Susanne Pfalzner, Amith Govind & Frank W. Wagner. In: The Astrophysical Journal Letters, 4 september 2024. [original (open access)]
