▁to ▁see ▁sources ▁in ▁the ▁southern ▁sky ; ▁a ▁ro cket ▁launched ▁from ▁Australia ▁will ▁not ▁be ▁able ▁to ▁see ▁sources ▁in ▁the ▁northern ▁sky . ▁ ▁X - ray ▁Quant um ▁Cal or imeter ▁( X Q C ) ▁project ▁ ▁In ▁astronom y , ▁the ▁inter stell ar ▁medium ▁( or ▁IS M ) ▁is ▁the ▁gas ▁and ▁cos mic ▁dust ▁that ▁per va de ▁inter stell ar ▁space : ▁the ▁matter ▁that ▁exists ▁between ▁the ▁star ▁systems ▁within ▁a ▁galax y . ▁It ▁fills ▁inter stell ar ▁space ▁and ▁bl ends ▁smooth ly ▁into ▁the ▁surrounding ▁inter gal actic ▁medium . ▁The ▁inter stell ar ▁medium ▁consists ▁of ▁an ▁extremely ▁dil ute ▁( by ▁terrest rial ▁standards ) ▁mixture ▁of ▁ ions , ▁atoms , ▁mole cules , ▁larger ▁dust ▁gra ins , ▁cos mic ▁ray s , ▁and ▁( gal actic ) ▁magnetic ▁fields . ▁The ▁energy ▁that ▁occup ies ▁the ▁same ▁volume , ▁in ▁the ▁form ▁of ▁elect romagnet ic ▁radiation , ▁is ▁the ▁inter stell ar ▁radiation ▁field . ▁ ▁Of ▁interest ▁is ▁the ▁hot ▁ion ized ▁medium ▁( H IM ) ▁consisting ▁of ▁a ▁cor onal ▁cloud ▁e jection ▁from ▁star ▁surfaces ▁at ▁ 1 0 6 - 1 0 7 ▁K ▁which ▁em its ▁X - ray s . ▁The ▁IS M ▁is ▁tur bul ent ▁and ▁full ▁of ▁structure ▁on ▁all ▁spatial ▁scales . ▁Stars ▁are ▁born ▁deep ▁inside ▁large ▁complex es ▁of ▁mole cular ▁clouds , ▁typically ▁a ▁few ▁parse cs ▁in ▁size