Tiny Pebbles Built the Gas Giant Behemoths

astroengine writes: Scientists have long puzzled over how gas planets like Jupiter and Saturn got to be so big. Current theories suggest the cores of these behemoths are comprised of mini-planets, some 62- to 620 miles in diameter, which collided and gradually merged together over time. But computer simulations show this process is more likely to produce hundreds of Earth-sized worlds. Instead, a new study suggests "slow pebble accretion" is a more likely process.