My understanding is the burgeoning gas giant eventually captures either an asteroid or remnant rocky debris which then grows through pebble accretion, but the gas giant would still be initially formed from mostly gases.
The (one) paper I read on this (while ignoring most of the confusing math bits) put the moons being captured when Jupiter was roughly 40% of its current mass.
CAPTURED POST FORMATION
COPE
SEEEEETHE
Removed by mod
My understanding is the burgeoning gas giant eventually captures either an asteroid or remnant rocky debris which then grows through pebble accretion, but the gas giant would still be initially formed from mostly gases.
The (one) paper I read on this (while ignoring most of the confusing math bits) put the moons being captured when Jupiter was roughly 40% of its current mass.