SUPERNOVAS,NEUTRON STARS, PULSARS, QUASARS, AND BLACK HOLES

The largest stars of all do not die quetly. Their higher gravity increases the temperature of central core to prodigious levels, so carbon is consumed to produce a succession of different element, and finnaly iron atoms, at its core. By this time, the internal reactions are consuming more energy than they produce. The star collapses and then explodes as a Supernova, increasing 
its brightness up to a billion times, and hurling more than half its matter out into space, procucing a nebua that will eventually help to form news stars and planets.

The most recent known supernova was seen on February 23, 1987, in the large Magellanic Cloud, a neightboring galaxy to the Milky Way. Left behind is the dense central core, shrinking from the blast of the explosion and its own internal gravity. So fierce a these compressive forces, that atoms are crushed into neutrons and star once larger than the Sun will collapse into a neutron star only a few mile across, and so dense that 
a spoonful of its matter would weigh hundreds of millions of tons.

Tough these neutron stars were predicted as long ago as the 1930s, they were not located until 1967, when radio astronomers observed a series of rapidly pulsing radio sources, which they called "pulsar." These pules were so regular and so rapid they could only be emmited from a small and fast - spinning object. Since the only bodies in the universe known to be small enough were neutron stars, it was almost certain that these were the misterious pulsars.

Brilliant objects called quasars, from quasi - stellar radio sources, appear like bright stars when photographed through optical telescopes, but also send out intense radio signals.
Consequently, they can be detected over thousands of 
millions of light years, and are now being seen as they were when the universe was young.
                           
Perhaps they are new galaxies in the procces of formation, or an early stage in theformation of the universe itself.