Editing Planetary core (section)

===Accretion===
Planetary systems form from flattened disks of dust and gas that [[Accretion (astrophysics)|accrete]] rapidly (within thousands of years) into [[planetesimal]]s around 10&nbsp;km in diameter. From here gravity takes over to produce Moon to Mars-sized [[planetary embryo]]s (10<sup>5</sup> – 10<sup>6</sup> years) and these develop into planetary bodies over an additional 10–100 million years.<ref name="Wood, Walter and Jonathan 2006">{{cite journal |last1=Wood |last2=Walter |last3=Jonathan |first1=Bernard J. |first2=Michael J. |first3=Wade |title=Accretion of the Earth and segregation of its core |journal=Nature |volume=441 |issue=7095 |date=June 2006 |pages=825–833 |doi=10.1038/nature04763|pmid=16778882 |bibcode = 2006Natur.441..825W |s2cid=8942975 }}</ref>

Jupiter and Saturn most likely formed around previously existing rocky and/or icy bodies, rendering these previous primordial planets into gas-giant cores.<ref name="Stevenson 1982" /> This is the [[accretion (astrophysics)|planetary core accretion]] model of planet formation.