2 Rising from the dust

The basis of the core-accretion scenario is that planets form by accumulation of solids into a core, on which an atmosphere is accreted once a critical value of the core mass is achieved. This section explores the various stages of this process, going from sub-micron-sized dust particles to metre-sized rocks that grow into kilometre-sized planetesimals and finally into Mercury-sized planetary embryos, spanning roughly 12 orders of magnitude in size. The embryos then accumulate further matter, becoming the cores of fully formed planets.