Although you might not think that the four planets in the Kepler-223 star system have anything in common with those in Earth's solar system, a new study reveals that the orbital configuration that holds together the system might have harbored Jupiter, Saturn, Uranus and Neptune in the early years of its existence before they broke free and embarked on a planetary migration.
"Exactly how and where planets form is an outstanding question in planetary science," said Sean Mills, a graduate student in astronomy and astrophysics at the University of Chicago and lead author of the study. "Our work essentially tests a model for planet formation for a type of planet we don't have in our solar system."
Mills and his team came to their conclusions using brightness data from NASA's Kepler telescope, which allowed them to determine how the four planets block starlight and affect each other's orbits. This allowed them to determine the planets' sizes and masses through inference and ultimately create simulations of the planetary migration that holds together the star system's current form.
The team discovered that the orbital configuration of the solar system has evolved since its birth 4.6 billion years ago, while the four known planets in the Kepler-223 system, which is much older, have remained in the same orbital configuration for much longer.
Scientists believe that it is possible that the larger, more distant planets in our solar system, such as Jupiter, Saturn, Uranus and Neptune, didn't remain stationary during their formation, instead moving around substantially. In fact, they could have originated in formations such as those seen in Kepler-223 until asteroids and small planets knocked them out of their orbital resonance.
"These resonances are extremely fragile," said Daniel Fabrycky, an assistant professor of astronomy and astrophysics at UChicago and co-author of the study. "If bodies were flying around and hitting each other, then they would have dislodged the planets from the resonance."
Tidal forces that rip planets from their solar systems' orbital configurations can also cause separation and planetary migration.
"Many of the multi-planet systems may start out in a chain of resonances like this, fragile as it is, meaning that those chains usually break on long timescales similar to those inferred for the solar system," Fabrycky said.
The findings were published in the May 11 issue of the journal Nature.
