At least 140 million Sun-like stars in our Milky Way galaxy may have experienced similar stellar flybys, according to a new study by astrophysicists from the Jülich Research Centre and Leiden University.
Snapshot of a flyby of an ancient star. Blue-green particles indicate TNOs injected into the planetary region by the flyby. The perturbation star passed through the disk at perihelion distance 110 AU, on the right side of the picture. Image courtesy of Pfalzner others., doi: 10.1038/s41550-024-02349-x.
The planets in our solar system accumulated from a disk of dust and gas orbiting the young Sun.
Thus, the planets move in circular orbits close to a common plane.
About 3,000 small bodies have been observed orbiting the Sun beyond Neptune. Surprisingly, most of them move in eccentric or inclined orbits.
Therefore, some force must have lifted these trans-solar objects (TNOs) out of the disk in which they formed and significantly altered their orbits.
“When we think about the solar system, we usually think of it ending with Neptune, the outermost known planet,” said Dr Susanne Pfalzner, astrophysicist at the Jülich Research Centre and lead author of the paper.
“However, thousands of objects are known to travel beyond the orbit of Neptune.”
“It is even suspected that there are tens of thousands of objects over 100 kilometers in diameter.”
“Surprisingly, many of these TNOs travel on eccentric orbits that are inclined with respect to the common orbital plane of the planets in our solar system.”
In this study, Dr. Falzner and her colleagues compared the properties of observed TNOs with thousands of flyby simulations to determine specific properties of stellar flybys that could potentially reproduce all of the different TNO populations, their locations, and relative abundances.
They Found A flyby of a 0.8 solar mass star at a distance of 110 AU could explain the inclined and highly eccentric orbits of known TNOs.
“We can even infer the orbits of very distant objects, such as Sedna, a dwarf planet discovered in the outermost solar system in 2003,” Dr Pfalzner said.
“There are also objects moving in orbits that are almost perpendicular to the planet's orbit.”
“Such flybys could even explain the orbits of two objects moving in the opposite direction to the planet: 2008 KV42 and 2011 KT19.”
“The best match we found in our simulations for the outer solar system today is a star that is slightly lighter than our Sun, about 0.8 times its mass,” said Dr Amis Govind, also of the Jülich research centre.
“It traveled about 16.5 billion kilometers from the Sun, which is about 110 times the distance between Earth and the Sun and just under four times the distance to the outermost planet, Neptune.”
Astrophysicists were surprised Found The irregular moons orbiting the giant planets in the solar system in distant, inclined, and eccentric orbits are actually TNOs that were launched into the inner solar system by close passes of their stars.
“Some of these objects could have been captured as moons by giant planets,” said Dr Simon Portegies Zwart, an astrophysicist at Leiden University.
“This would explain why the outer planets in our solar system have two different types of moons.”
“In contrast to regular moons, which orbit their planets in circular orbits close to the planet, irregular moons orbit their planets at greater distances in inclined, elongated orbits.”
“Until now, there has been no explanation for this phenomenon.”
“The beauty of this model is its simplicity. With just one source, it answers several outstanding questions about our solar system,” Dr Pfalzner said.
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Susanne Falzner othersOrbits of flybys of stars that formed the outer solar system. Nat AstronPublished online September 4, 2024; doi: 10.1038/s41550-024-02349-x
Susanne Falzner others2024. A close flyby of a star could inject an irregular moon from outside the solar system. Apu JL 972, L21;doi:10.3847/2041-8213/ad63a6
Source: www.sci.news
