In most planet formation theories, the boundary is around 10 Earth masses - the build up of the core mass before that is relatively slow, but once it crosses that threshold, the planet gains mass quickly via attracting gas from the surrounding nebula via the core’s gravitational pull, a process called “runaway accretion.” As this summary shows, you can ...
There are two common definitions in use for the surface of gas planets:
The 1-bar surface: As pressure increases, the deeper in we go into the gas planet, we will hit a pressure of 1 bar at some altitude. Gas at this altitudes will usually sit deep enough in the gravitational well and be of a near-uniform density and temperature, as to not be influenced by ...
The Kepler-20 system has planets with masses in the following order, going outwards from the star:
Kepler 20b: $\approx 10 M_\oplus$
Kepler 20e: $\approx M_\oplus$
Kepler 20c: $\approx 16 M_\oplus$
Kepler 20f: $\approx 1.5 M_\oplus$
Kepler 20g: $\approx 20 M_\oplus$
Kepler 20d: $< 20 M_\oplus$
If Wikipedia is to be believed, Kepler 20b may be a ...