Isaac Asimov's Novel The Currents of Space

As I wrote a couple of days ago, I'm currently in the processing of re-reading Isaac Asimov's Empire trilogy of novels.  I just finished the second one, titled The Currents of Space.  In it, Asimov speculates that it will be discovered that in deep space, "currents" exist that contain relatively large amounts of various elements.  Also, when a star system passes through a space current possessing a large amount of carbon, the star becomes a prime candidate for a nova explosion.  I don't think, however, that this is where we are nowadays with our understanding of novas...but for this story at least, we just have to play along with our good author's notions on the subject.  This is important because in the universe of Asimov's fictional future thousands of years from now, a specialist in the field of space currents has a dire warning to convey to the leaders of an inhabited planetary system...but unfortunately someone wipes his memory away (using something called a "psychic probe") before he can get his message across.  The story develops as he gradually recovers his memory while he and two companions are pursued by two conflicting sides: the locally dominant Sarks and the galactic empire of Trantor.  There is an important subplot to this tale, in which the planet of Florina is under Sark domination and whose inhabitants, of a lighter skin pigmentation than other people in general, are subjugated and suffer racial discrimination.  This is a not-so-oblique analogy to what was going on in America (especially in the South) with its racial segregation and prejudice of the mid-twentieth century, when The Currents of Space was written.  To leave no doubts in the minds of the reader about what he is doing, Asimov then has the oppressed people group forced to grow kyrt, which supposedly is a variant of cotton that grows better on that planet than anywhere else in the galaxy.  I guess back then this exposition against racial bigotry would have been considered a bold move on the author's part, but it seems somewhat patronizing and redundant to me now. 

The Empire series contains stories told with the backdrop of the growing Trantor Empire, each one transpiring a substantial time span after the previous.  With The Currents of Space, the Empire is strong but only covering about half our galaxy.  The third and final book of this series, titled Pebble in the Sky, has Trantor dominant throughout...