When they spin they release a electric kinetic beam at their poles and are called Pulsars.
As they grow old and split they may become magnetars spinning over 700 times a second.
Sometimes if they feed on a nearby star they could grow so much as to collapse further into a black hole.
The pulsar Neutron star may give us some clues as to the state of matter in black holes but we will never see it.

Speaking of new states of matter we have recently cooled/slowed matter more than deep space cold to 1/millionth of a degree which will make quantum computing more resilient.

Dark matter has been suggested to be composed of Fermions left over from the annihilation of matter and anti matter.


Other surprises that are not in text books yet are growing quickly.