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If you had followed the steps perfectly in "The Idiot's Guide to Building a Solar System", you would end up with a star surrounded by a flat disk of planetary material, orbiting in relatively neat, circular paths. But our solar system's disk is quite distorted: the orbits of its planets are slightly tilted and more oval than circular. So what happened?
A massive object is thought to have entered the solar system early in its formation, leaving a lasting mark on the orbits of the planets before disappearing back into space, according to a new study by University of Toronto physicists Garrett Brown and Hanno Rhine, in collaboration with planetary scientist Renu Malhotra of the University of Arizona.
Solar System Diagrams
Don't be fooled by the diagrams - our solar system's orbits are far from perfectly circular or flat. Even under favorable galactic conditions, the odds of this happening are only about 1 in 1 - not enough to be a definitive explanation, but the hypothesis is worth considering if supporting evidence emerges.
It's now pretty clear that objects from outside our solar system occasionally hurtle toward the Sun, usually picking up enough speed at astronomical distances to escape back into space. In 2017, the asteroid Oumuamua entered and exited our solar system, giving astronomers the perfect opportunity to reflect on the long history of interstellar visitors.
What if something heavier crossed our solar system?
But the presence of 'Oumuamua is just a drop in the bucket. What if a much more massive object were to pass through the waters of the Solar System?
Brown, Rhine, and Malhotra performed calculations and concluded that an object with a mass between 2 and 50 Jupiter masses, moving on a curved trajectory around the Sun within the orbit of Uranus at a speed sufficient for escape, could move the giant planets into orbits similar to those we see today.
After refining their models through simulations of about 50 variations, they found that the best explanation for our planets' eccentric orbits was an object with a mass of just over 000 Jupiter masses approaching the current orbit of Mars at a speed of 8 km/s. Further simulations showed that in 2,69% of cases, one of our planets could be ejected from the Solar System within the next 2 million years. In other cases, the inner planets remained in slightly altered but still harmonious orbits.
A rare but not impossible event
Although the probability of such an event is low – 1 in 1 to 000 in 1 – the possibilities for such a scenario may not be so rare, given that there are many suitable star clusters in the Milky Way.
“In other words, we don’t have to look for a needle in a haystack to find a suitable collision,” the authors write in the study, which has not yet been peer-reviewed.
With the nearest star being over 4 light-years away, it's easy to imagine our solar system as relatively isolated. But like our planet, the Sun moves on a path that periodically brings it closer to other stars and star clusters, as well as to the cold, dark planets that roam interstellar space.
What awaits our Solar System?
What the future holds for our bizarre family of planets remains unknown. But there is a small chance that one day the solar system will become even more twisted than it is now. The research is available on the arXiv preprint server.
