Black holes 'dodge middle ground'

Middleweight black holes were thought to be hiding in globular clusters

For black holes, there appears to be very little room for mediocrity, astronomers have found.

A study suggests they come in either small or large sizes, but medium-sized ones are very rare or non-existent. A team of astronomers has examined one of the best hiding places for a middleweight black hole, and found that it cannot possibly host one. Details of the research are to be published in the latest issue of the Astrophysical Journal. - bbc