Sphero Nova

They came out of the star-strewn wilderness around Sol, these alien creatures. And their object was the vicious, total destruction of the Federation of Worlds. Earth was one of the last pf the planets to be attacked and here they were opposed by the Earth Council: six men who held the destinies of a hundred billion people in their hands. But in the end, there remained only one man out of the six to fight.
Velga Dorne, Earth Councillor and Member of the Triumvirate of Worlds. And he himself was a hunted man. Death and terrible destruction followed him across the wastes of space in the search for the crazy, nightmare planet that had spawned these creatures. Fear and terror were his only companions. Until he reached the nameless planet of a still more insignificant sun and learned that there were others to join him in the struggle against the black, inhuman monsters.
These were the Hheroni, scientists whose achievements had progressed along a slightly different path of research to humanity. And Astraea, the girl who went with him on the suicidal mission to where the Aliens originated: on a world that no one in their wildest dreams had thought possible to exist, one which even science said was impossible.