you-RAY-nus is the correct pronounciation. Sagan was also wrong about Comet "Hal-lee" (in England, Edmund Halley pronounced it "Hall ee", as in kids in the), among other things.
I'm very sorry but I've been an amateur astronomer for 25 years and "u RAY nus" is not the correct pronounciation. You are simply wrong but, as I said, who am I to spoil a childish joke for those who enjoy such things.