<P> In globular clusters a few stars known as blue stragglers are observed, apparently continuing the main sequence in the direction of brighter, bluer stars . The origins of these stars is still unclear, but most models suggest that these stars are the result of mass transfer in multiple star systems . </P> <P> In contrast to open clusters, most globular clusters remain gravitationally bound for time periods comparable to the life spans of the majority of their stars . However, a possible exception is when strong tidal interactions with other large masses result in the dispersal of the stars . </P> <P> After they are formed, the stars in the globular cluster begin to interact gravitationally with each other . As a result, the velocity vectors of the stars are steadily modified, and the stars lose any history of their original velocity . The characteristic interval for this to occur is the relaxation time . This is related to the characteristic length of time a star needs to cross the cluster as well as the number of stellar masses in the system . The value of the relaxation time varies by cluster, but the mean value is on the order of 10 years . </P> <Table> Ellipticity of globular clusters <Tr> <Th> Galaxy </Th> <Th> Ellipticity </Th> </Tr> <Tr> <Td> Milky Way </Td> <Td> 0.07 ± 0.04 </Td> </Tr> <Tr> <Td> LMC </Td> <Td> 0.16 ± 0.05 </Td> </Tr> <Tr> <Td> SMC </Td> <Td> 0.19 ± 0.06 </Td> </Tr> <Tr> <Td> M31 </Td> <Td> 0.09 ± 0.04 </Td> </Tr> </Table>

Who was the first to measure the structure of milky way using globular clusters