The team, headed by astronomer Lauren Weiss PhD, found the phenomenon endures irrespective of the type of star planets orbit. The 909 planets analyzed reside in 355 systems in total, each of which was discovered by the Kepler space telescope.
Named after astronomer Johannes Kepler, the spacecraft was launched March 7, 2009 — it aims to discover Earth-size exoplanets in or near habitable zones, and estimate how many of the billions of stars in the Milky Way have such planets.
On May 10, 2016, NASA verified 1,284 new exoplanets found by Kepler, the single largest finding of planets to date.
Studying planet demographics w/ @NASAKepler, astronomers find small planets w/in 1AU have 2 major size groupings, divided at ~1.8 earth-rad. pic.twitter.com/OxciAy3mYC
— Natalie Batalha (@nbatalha) June 24, 2017
Current theories of how star systems are forged suggest stars first form from a cloud of gas and dust, creating a thick disc — then, within that disc, then denser clusters of gas and dust condense into planets. In essence, the shape and size of a star should directly dictate how its accompanying system is composed.
Now however, the team's finding that star systems are seemingly homogenous in composition indicates something other than stellar mass influences how protoplanetary discs give rise to planets — perhaps the total mass of the disc, the solid mass within the disc or the physics of the disc that planets form in.
Lauren Weiss on multiplanet systems: solar system is similar to Kepler multis in terms of dynamical compactness #KeplerSciCon pic.twitter.com/fkSGi9Bw5x
— Zafar Rustamkulov (@ExoZafar) June 23, 2017
However, it may conversely be possible this pattern is not a pattern at all, but in fact pattern recognition, produced by limited data.
The astronomer's team could only analyze planets with short orbital periods, which crossed in front of their star during Kepler's four year mission — it would be akin to basing a conclusion about Alpha Centauri after only studying Mercury, Venus, Earth and Mars.
Nonetheless, the team intends to move forward with their research, and attempt to confirm their seeming discovery.
Further theories may already be being built around their potential observation — among them perhaps, that the third planet from the sun in other star systems hosts, or is capable of hosting, life.
