With the advent of new technologies of the 1960s and 1970s, particularly with space technology, man’s vision of the universe increased hundredfold and an awe inspiring view of hosts of otherwise unseen objects like quasars, pulsars, X-ray binaries and active galactic nucleii became a part of our universe. Most of these objects emit radiation in almost all known frequencies of the electromagnetic spectrum, with luminosities ranging from few times to few thousand times the galactic emission.