"If the Moon was closer, the COG would have been nearer the centre of the Earth.

The COG will only emerge above Earth's surface when the ratio of the Moon's orbit radius to Earth's radius exceeds the ratio of Masses.

Mass ratio is 1:81

Current radius ratio is 1:15.9

Therefore the Moon needs to retreat to ~ 2,035,000 km (5 times its present distance), before the barycentre is outside the body of the Earth."

Oh. I got it backwards, huh:)
Hmm, ok, so Pluto is 2274 km in diameter and has mass of 1.27e22 kg.
Charon is 1172 km in diameter and has mass of 1.90e21 kg and is 19,640 km from Pluto.
And from 9 planets we have this quote:
"Though the sum of the masses of Pluto and Charon is known pretty well (it can be determined from careful measurements of the period and radius of Charon's orbit and basic physics) the individual masses of Pluto and Charon are difficult to determine because that requires determining their mutual motions around the center of mass of the system which requires much finer measurements -- they're so small and far away that even HST has difficulty. The ratio of their masses is probably somewhere between 0.084 and 0.157; more observations are underway but we won't get really accurate data until a spacecraft is sent."
So roughly we could say the Mass ratio is 1:10
Taking the radius of 1137 km of Pluto and orbital radius of 19,640
The radius ratio is what?
Earth radius is 6378 km and Moon orbiting radius 384,000 km which seems to be about 60 earth radius to the Moon.
And same with Pluto & Charon, gives 17 Pluto radius to Charon.
So I guess the barycentre of Pluto & Charon is in space, though if the orbit is highly eclipital, it might dip into Pluto?
What happens if barycentre is at the atmosphere height of some planet?