308 FBOM NEBULA TO NEBULA 



minimum brilliancy at or very near the time when the bright star 

 in the system has its maximum velocity of recession from the 

 solar system. These are keys which give promise of unlocking 

 many secrets of the Cepheids and Geminids. What can be more 

 remarkable than that variable stars of this class should be at their 

 brightest when they are moving rapidly toward the observer and 

 at their faintest when they are moving rapidly away from himf 



THE NEBULAE 



Nebulae are at once the ghosts of departed stars and 

 the corpora of other stars yet to be born. They are not 

 primordial, but transitional forms; the first star pre- 

 ceded the first nebula. They differ fundamentally from 

 the original cosmic dust in having passed through the 

 stellar crucible and consequently undergone considerable 

 chemical rearrangement and combination. Further- 

 more, although much of it may have been lost in the cata- 

 clysms that gave them birth, they retain in their nebulous 

 condition some remnant of the motion possessed by them 

 as member stars of the systems that have vanished. 



Owing to their explosive origin, nebulae are naturally 

 capricious and nondescript in form, and there is little to 

 be learned from their incipient shapes. Their sizes, how- 

 ever, vary so widely as to demand categorical explana- 

 tion. I have already recounted at length the production 

 of the smaller nebulae by the spontaneous explosion or 

 puncturing of stars, and of large nebulae by the bursting 

 of maximum-sized stars from sheer over-growth. All 

 of these, however, might perhaps result in rather too 

 simple and regular forms to suit every nebular outline, 

 and there might remain also a doubt as to whether the 

 destruction of even the biggest star would commensurate 

 with the size of the biggest nebula. To account for the 

 extraordinary cases, then, such as Eta Argus or Orion, 

 for example, I suggest that the explosion of some mon- 

 ster star in the near vicinity (as stellar distances go) of 

 a cluster of other large stars might cause the puncture 

 of several more, each succeeding explosion, moreover, 

 creating a new center of destruction. In this way (my 



