In order to study the small-scale structure of the hot interstellar gas , we obtained Far Ultraviolet Spectroscopic Explorer interstellar O VI interstellar absorption spectra of 4 four post-extreme horizontal branch stars in the globular cluster NGC 6752 [ ( l,b ) = ( 336 \fdg 50 , -25 \fdg 63 ) , d = 3.9 kpc , z = -1.7 kpc ] .
The good quality spectra of these stars allow us to measure both lines of the O VI doublet at 1031.926 Å and 1037.617 Å .
The close proximity of these stars permits us to probe the hot interstellar gas over angular scale of only 2 \farcm 2 - 8 \farcm 9 , corresponding to spatial scales \lesssim 2.5 - 10.1 pc .
On these scales we detect no variations in the O VI column density and velocity distribution .
The average column density is \log \langle N ( { \mbox { O$ $ { \small VI } } } ) \rangle = 14.34 \pm 0.02 ( \log \langle N _ { \perp } ( { \mbox { O$ $ { \small VI } } } ) \rangle = 13.98 ) .
The measured velocity dispersions of the O VI absorption are also indistinguishable .
Including the earlier results of Howk et al. , this study suggests that interstellar O VI is smooth on scales \Delta \theta \lesssim 12 \arcmin , corresponding to a spatial scale of \lesssim 10 pc , and quite patchy at larger scales .
Although such small scales are only probed in a few directions , this suggests a characteristic size scale for the regions producing collisionally-ionized O VI in the Galaxy .