A recently-discovered group of four planets located in a system in the constellation Cygnus have orbits so closely synchronized with one another that it provides long-term stability for the system they call home, according to research published Wednesday in the journal Nature.
This extrasolar planetary system, Kepler-223, was discovered by NASA’s planet-hunting Kepler mission, and the new study had revealed that the orbital periods of the four planets align with one another, having ratios of 3 to 4, 4 to 6 and 6 to 8, according to the authors.
The Kepler-223 planets “interact gravitationally to keep the beat of a carefully choreographed dance as they orbit their host star,” research team member Eric Ford, a professor of astronomy and astrophysics at Penn State University, explained in a statement. This enables the system to have “unusually long-term stability,” he and his colleagues explained in their paper.
For instance, whenever the innermost planet (Kepler-223b) orbits the system’s central star three times, the second-closest planet (Kepler-223c) completes precisely four orbits, which means that both worlds return to the same positions relative to each other and their host star at the end of the process. This synchronization acts like a stabilizing influence for the system.
Observations provide clues as to how these planets formed
This orbital synchronicity also provides strong clues” about “how its planets could have formed,” Ford said. “Our analysis shows that a slow, smooth, migration of the system during its formation and evolution would be able to place these planets into the delicately balanced configuration that we observe today,” he explained.
Systems such as this provide astronomers and astrophysicists with a rare opportunity to test out various different models of planetary formation, and the team’ findings could have implications for other planetary systems as well. In fact, they noted that the system’s current set up is similar to the migration patterns suspected for out solar system’s four outermost planets.
“Kepler found lots of systems with multiple super-Earth and/or sub-Neptune-size planets orbiting close to their host star, but the vast majority of these systems are not in a special resonant configuration like that of Kepler-223,” said Ford. “Many of these systems may have formed similarly to Kepler–223, but then later became destabilized, perhaps by a more distant massive planet or perhaps by the cumulative effect of the scattering of many smaller planetesimals left over from the planet-building process.”
He and his colleagues used data from the Kepler telescope to measure the amount of starlight blocked by each of the planets as the transit (pass in front of) their host star, as well as to detect miniscule changes in each of the planet’s orbits. By combining this data with other observations, they were able to determine the size and mass of each of the planets.
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Image credit: NASA Ames Research Center/Kepler Mission
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