Queen's University researcher Martin Duncan has co-authored a study that solves the mystery of how gas giants such as Jupiter and Saturn formed in the early solar system. In a paper published this week in the journal Nature, Dr. Duncan, along with co-authors Harold Levison and Katherine Kretke (Southwest Research Institute), explain how the cores of gas giants formed through the accumulation of small, centimetre- to metre-sized, "pebbles.

"As far as we know, this is the first model to reproduce the structure of the outer solar system - two gas giants, two ice giants (Uranus and Neptune), and a pristine Kuiper belt beyond Neptune," says Dr. Duncan.

The currently accepted, "standard model" states that these cores formed through collisions between much larger bodies 100-1,000 kilometres in size, known as planetesimals. However, this model would not have allowed the cores to form quickly enough to capture the gases that make up their atmosphere in the early solar system.

The model created by Dr. Duncan and his team shows that collisions and accumulation of the so-called pebbles would have allowed the cores to form much more rapidly. In addition, the new model accurately predicts the formation of one to four gas giant planets; consistent with what we see in the outer solar system.

"It is a relief, after many years of performing computer simulations of the standard model without success, to find a new model which is so successful," says Dr. Duncan.

Read the study, Growing the Gas-Giant Planets by the Gradual Accumulation of Pebbles in Nature.