▁free - of - charge ▁ride . ▁ ▁There ▁are ▁major ▁limitations ▁to ▁am ateurs ▁obser ving ▁and ▁reporting ▁experiments ▁in ▁X - ray ▁astronom y : ▁the ▁cost ▁of ▁building ▁an ▁amateur ▁ro cket ▁or ▁bal lo on ▁to ▁place ▁a ▁det ector ▁high ▁enough ▁and ▁the ▁cost ▁of ▁appropriate ▁parts ▁to ▁build ▁a ▁suitable ▁X - ray ▁det ector . ▁ ▁History ▁of ▁X - ray ▁astronom y ▁ ▁In ▁ 1 9 2 7 , ▁E . O . ▁H ul b urt ▁of ▁the ▁US ▁Naval ▁Research ▁Labor atory ▁and ▁associ ates ▁Gregory ▁Bre it ▁and ▁Mer le ▁A . ▁Tu ve ▁of ▁the ▁Car neg ie ▁Institution ▁of ▁Washington ▁expl ored ▁the ▁possibility ▁of ▁equ ipping ▁Robert ▁H . ▁God d ard ' s ▁rock ets ▁to ▁explore ▁the ▁upper ▁atmosphere . ▁" Two ▁years ▁later , ▁he ▁proposed ▁an ▁experimental ▁program ▁in ▁which ▁a ▁ro cket ▁might ▁be ▁instrument ed ▁to ▁explore ▁the ▁upper ▁atmosphere , ▁including ▁detection ▁of ▁ult rav io let ▁radiation ▁and ▁X - ray s ▁at ▁high ▁alt itudes ". ▁ ▁In ▁the ▁late ▁ 1 9 3 0 s , ▁the ▁presence ▁of ▁a ▁very ▁hot , ▁ten uous ▁gas ▁surrounding ▁the ▁Sun ▁was ▁infer red ▁indirect ly ▁from ▁optical ▁cor onal ▁lines ▁of ▁highly ▁ion ized ▁species . ▁The ▁Sun ▁has ▁been ▁known ▁to ▁be ▁surrounded ▁by ▁a ▁hot ▁ten uous ▁cor ona . ▁In ▁the ▁mid - 1 9 4 0 s ▁radio ▁observations ▁revealed ▁a ▁radio ▁cor ona ▁around