▁the ▁Lock man ▁H ole , ▁it ▁is ▁a ▁relatively ▁clear ▁" window " ▁through ▁the ▁u bi quit ous ▁clouds ▁of ▁neutral ▁hydro gen ▁gas ▁in ▁our ▁Mil ky ▁Way ▁galax y , ▁which ▁allows ▁us ▁to ▁clearly ▁see ▁the ▁rest ▁of ▁the ▁universe ▁in ▁X - ray s . ▁ ▁The ▁image ▁is ▁centered ▁on ▁RA ▁ ▁DE C ▁ ▁( J 2 0 0 0 . 0 ), ▁covering ▁ 0 . 1 1 ▁square ▁degrees , ▁meas uring ▁ 1 6 ▁arc min utes ▁across . ▁This ▁patch ▁of ▁sky ▁lies ▁in ▁the ▁For na x ▁const ell ation . ▁ ▁The ▁image ▁was ▁created ▁by ▁compos iting ▁ 1 1 ▁individual ▁AC IS - I ▁expos ures ▁for ▁a ▁cum ulative ▁expos ure ▁time ▁of ▁over ▁one ▁million ▁seconds , ▁in ▁the ▁period ▁ 1 9 9 9 - 2 0 0 0 , ▁by ▁a ▁team ▁led ▁by ▁Ric c ardo ▁G iac con i . ▁This ▁region ▁was ▁selected ▁for ▁observation ▁because ▁it ▁has ▁much ▁less ▁gal actic ▁gas ▁and ▁dust ▁to ▁obsc ure ▁distant ▁sources . ▁Further ▁observations ▁taken ▁between ▁ 2 0 0 0 ▁and ▁ 2 0 1 0 ▁have ▁resulted ▁in ▁a ▁total ▁of ▁expos ure ▁of ▁over ▁four ▁million ▁seconds . ▁An ▁additional ▁four ▁million ▁seconds ▁of ▁expos ure ▁are ▁scheduled ▁to ▁be ▁undert aken ▁by ▁the ▁end ▁of ▁ 2 0 1 5 , ▁resulting ▁in ▁an ▁integrated ▁expos ure ▁time ▁of ▁eight ▁million ▁seconds . ▁The ▁Ch andra ▁Deep