A cosmic object the size of a planet would have passed through the Solar System and permanently changed the orbits of four planets, according to a new study not yet published in the peer-review regime, based on computer simulations, reports Live Science on Sunday.
The soalr system PHOTO: The truth (archive)
This hypothesis could explain why the orbits of the Jovian planets present some features considered less common,
For decades astronomers have debated how the planets of the Solar System formed. But most hypotheses agree on the type of orbit the planets should have: circles arranged concentrically around the Sun in the same plane. But none of the 9 planets, including Earth, have perfectly circular orbits. In addition, these orbits are not in the same plane with each other, writes Agerpres.
Compared to Mercury, whose orbit is the most elongated and inclined of the four telluric planets of the Solar System, the orbits of the four Jovian planets – Jupiter, Saturn, Uranus and Neptune – present minor deviations from the ideal orbits. Explaining these discrepancies is difficult, according to Renu Malhotra, a planetary scientist at the University of Arizona and co-author of the new study.
“A puzzle for astrophysicists has long been how the orbits subsequently became more elongated and inclined to the main plane by not too much, but not too little,” she writes in an email to Live Science. While previous studies focused on how interactions between these planets would have changed their orbits, “these hypotheses do not explain certain important details of the observed orbits,” according to Malhotra.
To solve this enigma, Malhotra and his colleagues started from a less examined scenario: namely, that a wandering cosmic object, the size of a star, would have modified the orbits of these planets about 4 billion years ago.
Using computer models of the 4 Jovian planets, the team ran 50,000 simulations of such transits, each over 20 million years, changing one by one the parameters of the cosmic object that could have passed through the early Solar System – such as speed, mass and how close it could have been to the Sun.
The researchers also took into account objects with smaller masses than stellar ones, similar, for example, to the giant planet Jupiter. Scenarios where the errant object would have passed less than 20 AU from the Sun – (astronomical units: 1 AU = 150 million kilometers or the average distance from the Earth to the Sun) were also taken into analysis.
Although most of the simulations resulted in conditions very different from those of the present day in the Solar System, the researchers noticed that in about 1% of the simulations, the passage of the errant cosmic object changed the orbits of the giant planets resulting in variations similar to those observed by astronomers.
In these scenarios, the errant cosmic object plunged straight through the Solar System, passing well beyond the orbit of Uranus, and in some scenarios almost intersecting the orbit of Mercury. Such an object was much smaller than a star, having a mass between 2 times and up to 50 times that of the planet Jupiter.
“In this interval there are planetary mass objects and even brown dwarfs”, according to Malhotra. Brown dwarfs, often called “missing stars” are cosmic objects with masses greater than planetary masses, but smaller than stellar masses.
The simulation that produced the closest results was that of an object that had 8 times the mass of the planet Jupiter and came as close as 1.69 AU from the Sun (slightly further than the orbit of Mars at 1.5 AU) .
