There are two basic theories on planet formation. One is thatAnd Stars would not split in half, it would likely shoot out a streamer of "core material" that is of a different charge than its surface material. This material (mass ejection) would pile up at a certain altitude and be pinched into a sphere... Likely many other "globules" would also harden into planetlike objects and would begin to orbit the old or new sun.
stars get too much electrical stress and split in halves, forming
the binary systems that are so common. During this process
the core of the star may be elongated and break up forming
a planet or many planets which are held between the stars by
electrical forces, or possibly by the rotation of the binary system
balancing either electrical or gravitational forces. This sort of
planet could be hollow.
The other theory is that gas giants or brown dwarfs or stars
eject material which become planets like Venus. One theorises
that a plasma current enters the surface of Saturn, say, and
pulls on the planet extracting this material that forms a planet.
If so, then this current could go through the centre of this
material and a hollow planet could again eventuate. Another
intriguing possibility is that this material comes not from the
core of Saturn, but from the surface. Thus Saturn would be a
hollow planet with a solid surface that was fairly thin. Then it
would be fairly easy to remove a chunk of this surface material.
Just maybe the 'heavy' elements, formed by the electrical
discharges on the surface of a star or brown dwarf or gas
giant, don't fall to the core, but rather congeal at the surface.
It's a wonderful world of theory here !