The Romance of the Heavens 43 



be seen at such a distance. The new star had increased its light 

 many hundredfold in a few days. 



There is a considerable fascination about the speculation 

 that in such cases we see the resurrection of a dead world, a means 

 of renewing the population of the universe. What happens is 

 that in some region of the sky where no star, or only a very faint 

 star, had been registered on our charts, we almost suddenly per- 

 ceive a bright star. In a few days it may rise to the highest 

 brilliancy. By the spectroscope we learn that this distant blaze 

 means a prodigious outpour of white-hot hydrogen at hundreds 

 of miles a second. But the star sinks again after a few months, 

 and we then find a nebula round it on every side. It is natural to 

 suppose that a dead or dying sun has somehow been reconverted 

 in whole or in part into a nebula. A few astronomers think that 

 it may have partially collided with another star, or approached 

 too closely to another, with the result we described on an earlier 

 page. The general opinion now is that a faint or dead star had 

 rushed into one of those regions of space in which there are 

 immense stretches of nebulous matter, and been (at least in part) 

 vaporised by the friction. 



But the difficulties are considerable, and some astronomers 

 prefer to think that the blazing star may merely have lit up a 

 dark nebula which already existed. It is one of those problems on 

 which speculation is most tempting but positive knowledge is 

 still very incomplete. We may be content, even proud, that 

 already we can take a conflagration that has occurred more than 

 a thousand trillion miles away and analyse it positively into an 

 outflame of glowing hydrogen gas at so many miles a second. 



THE SHAPE OF OUR UNIVERSE 



4 

 Our Universe a Spiral Nebula 



What is the shape of our universe, and what are its dimen- 

 sions? This is a tremendous question to ask. It is like asking 



