Neutron Stars and Black Holes

NEUTRON STARS AND BLACK HOLES form from the stellar cores that remain after stars have exploded as spernovave.If the remaining core is between about one and a half of and three solar masses,it contrast to form a neutron star.If the remaining core is greater than about three solar masses ,it contract to form a black hole.

Neutron star are typically only about 10 kilometers in diamter and consist almost entirely of  subatomic particles called neutrons.Such stars are so dense that a tea teaspoonful would weigh about a billion tonnes.Neutron sta are observed as pulsers,so called because they rotate rapidly and emit two beams of radio waves which sweeps across the sky and are directed as short pulses.

black holes are characterised by their strong gravity,which is so powerfull even a light cannot escape;as a result black holes are invisible.how ever it can be detected if there is a close companion star.The gravity of the star pulls the gas from the other star,farming an accretion disc that spirals arround the black hole at high speed,heating up and emmiting radiation.eventually the matter spirals into cross the event horzon(the boundar of the black hole),There by disappearing from the visible universe.