Evacuation of gas from globular clusters by winds from millisecond pulsars

WHY is so little gas observed within globular clusters? A typical globular cluster contains ∼10³ post-turn off stars, each of which will lose ∼0.2M_⊙ before its asymptotic giant branch phase of evolution, and ∼0.1M_⊙ during this phase¹, and so should accumu-late 10²∼10³M_⊙ of gas in the 10⁸-year interval between passages of the globular cluster through the galactic disk. (At each disk passage, gas ram pressure will remove the accumulated material^2,3.) But observational searches show that there is scant intracluster gas; in many clusters, there is less than 1M_⊙ of gas, orders of magnitude less than theoretical predictions³. The recent discovery^4,5 of multiple millisecond pulsars in globular clusters may resolve this long-standing problem: the relativistic wind from these pulsars is enough to drive gas from stellar mass loss out of the globular cluster.