Quasars - the Remotest Objects in the Universe?

In 1963 astronomers identified ' quasars ' - star-like objects which were held to be the most remote and the most luminous ever seen. There have been doubts about the accuracy of these estimates, but new research indicates that it is correct. Patrick Moore talks to Dr Simon Mitton , of Cambridge University, about these strange objects which may well lie very close to the edge of the observable universe.