PAPERS PRESENTED AT GENERAL SESSIONS 73 



will arrive at the borders of the galaxy in less than twen- 

 ty-seven millions of years with a speed of sixty-five 

 kilometers per second, and ^\^11 leave the galaxy never to 

 retnrn. Such stars are called run-a-way stars, and more 

 than fifty of them, perhaps, are known, with speeds as 

 high as 300 kilometers per second and even higher. They 

 tell us in unmistakeable tenns that intergalactic space is 

 not altogether devoid of stars which pursue their lonely 

 way without attachment to any partixjular system. They 

 are truly ''lost Pleiads." 



Let us assume that a large region of extra-galactic 

 space has become nebulous by virtue of the radiant en- 

 ergy which has long been passing through it. Eventually, 

 one of our "'lost Pleiads" enters the region. It begins 

 to grow in mass and to diminish in speed. If the speed is 

 sufficiently reduced, the star will be unable to escape from 

 the gi^avitational control of the nebula and it becomes 

 permanently attached to the nebula. Other stars are 

 caught and held similarly so that in the course of time 

 a region that was purely nebulous becomes a cluster of 

 stars. If the stars came from all directions at random 

 the cluster would have little or no tendency to rotate as a 

 whole, and it would finally attain the forms of equilibri- 

 um which we recognize as the globular star clusters. If 

 we imagine a loosely connected series of such nebulous re- 

 gions, each one of which in time becomes a star cloud by 

 the capture of wandering stars, and if we assume that the 

 whole mass has an angular momentum about the common 

 center of gravity, it is easy to see how the mass added by 

 the captured stars would make the clouds draw closer 

 together and build up such a wonderful system of stars 

 as we find in the galaxy itself. Indeed, as the region 

 '^"ithin the galaxy is still somewhat nebulous it is evident 

 that the galaxy has not yet altogether lost its capacity 

 for capture. Eventually, however, the mass will decline 

 through the radiation of its energies. The gravitative 

 control of the cluster upon its individual members will 

 relax, the cluster expands until, one by one, the stars 

 escape the group control and resume once more their 

 lonely wanderings. 



