210 PROGRESS OF SCIENCE IN THE CENTURY. 



factor in the production of the sun's lieat has been 

 suggested by several astronomers. 



Sir Robert Ball illustrates this by the story of the 

 new star in Auriga, whose appearance was observed 

 in February, 1892. Where a few days before the 

 photographic plates had shown nothing, a bright 

 star suddenly became apparent. " Everything we 

 have learned about the matter suggests that the new 

 star in Auriga during the time of its greatest bril- 

 liance dispersed a lustre not inferior to that of our 

 own sun. ... It became clear that the brightness 

 of the new star in Auriga was the result of a collision 

 which had taken place between two previously ob- 

 scure bodies. Perhaps it would hardly be right to 

 describe what happened as an actual collision. It 

 is, however, perfectly clear from the evidence that 

 two objects, whose relative velocities were some 

 hundreds of miles to a second, came into such close 

 proximity that by their mutual action a large part 

 of their energy of movement was transformed into 

 heat, and a terrific outburst of incandescent gases 

 and vapours proclaimed far and wide throughout 

 the universe the fact that such an encounter had 

 taken place." * 



From the analogy of Nova Aurigce — which is no 

 isolated instance — it has been conjectured, by Lord 

 Kelvin among others, that our sun may have arisen 

 from the collision of two bodies which attracted 

 each other until they became a single sun with an 

 enormous store of heat derived from the crash of 

 their impact. 



This speculation is of interest when we look 

 forward to the time in the life of a sun or star, when 

 further compression no longer compensates for the 



* Sir Robert Ball, loccit, p. 277. 



