Another scientific mystery in Baha'u'llah's day was whether stars other than our own sun have planets. Baha'u'llah Himself was very explicit: 'Every fixed star', He wrote, 'hath its own planets...' (The traditional term 'fixed star' refers to self-luminous stellar bodies like our own sun, in contrast to planets that once were called 'wandering stars'.) Throughout most of our present century astronomers insisted that planets cannot occur naturally but only as a result of some freak catastrophe such as a near- collision between stars. Not until the early 1970s did new mathematical models show that the rotation of a star necessarily spins off a disk of matter, forming rings that coalesce into orbiting bodies. According to current knowledge, then, every normal star will at some point sire planets as part of its natural life- cycle.