From Protoplanetary Disks to Gas Giants: Kepler Data Reveals Distinct Paths of Planet Formation
Analysis of data harvested by the Kepler telescope has shed new light on the origins of exoplanets, revealing why planets of varying sizes follow such different cosmic journeys. Smaller worlds—those lighter and tinier than Neptune, roughly 17 times Earth’s mass—tend to trace near-perfect circles around their stars. In contrast, heftier gas giants often sweep along stretched, elliptical orbits. Another striking pattern emerged: massive planets frequently orbit stars brimming with metals—elements like oxygen, carbon, and iron—while the chemical makeup of a star seems less consequential for their smaller kin.
This breakthrough stems from a study by researchers at the University of California, Los Angeles (UCLA), who sifted through Kepler’s observations of 150,000 stars, collected between 2009 and 2018. From this vast trove, they honed in on 1,600 light curves—graphs charting the dips in stellar brightness as planets glide past. To ensure precision, the team meticulously reviewed each curve by hand and crafted custom tools to bring the data to life. Their findings point to a fundamental divide: small and large planets are born through starkly different processes.
A fresh theory suggests that petite planets take shape within protoplanetary disks—swirling clouds of gas and dust encircling young stars—through the slow clumping of tiny fragments and particles. Gas giants, however, embark on a bolder path. They begin with a hefty core, exceeding 10 Earth masses, which swiftly siphons gas from the disk to balloon into a colossal world. This transformation, though, hinges on a metal-rich star. Over time, the gravitational heft of these giants can unsettle their systems, tugging their orbits into elongated ellipses and occasionally sparking planetary collisions.
