y ▁ 1 8 ▁is ▁a ▁d war f ▁irregular ▁galax y ▁located ▁about ▁ 5 9 ▁million ▁light ▁years ▁away ▁in ▁the ▁const ell ation ▁Urs a ▁Major . ▁The ▁galax y ▁was ▁first ▁identified ▁by ▁Swiss ▁astronom er ▁Fritz ▁Z wick y ▁in ▁a ▁ 1 9 3 0 s ▁phot ographic ▁survey ▁of ▁galaxies . ▁ ▁Age ▁Studies ▁at ▁the ▁Pal om ar ▁Observ atory ▁some ▁ 4 0 ▁years ▁ago ▁led ▁astronom ers ▁to ▁believe ▁that ▁the ▁galax y ▁er upt ed ▁with ▁star ▁formation ▁bill ions ▁of ▁years ▁after ▁its ▁gal actic ▁neighb ors . ▁Gal ax ies ▁res emb ling ▁I ▁Z wick y ▁ 1 8 ' s ▁youth ful ▁appearance ▁are ▁typically ▁found ▁only ▁in ▁the ▁early ▁universe . ▁Early ▁observations ▁with ▁the ▁Hub ble ▁Space ▁T eles cope ▁suggested ▁an ▁age ▁of ▁ 5 0 0 ▁million ▁years ▁old ▁for ▁I ▁Z wick y ▁ 1 8 . ▁The ▁Hub ble ▁Space ▁T eles cope , ▁however , ▁later ▁found ▁faint , ▁older ▁stars ▁contained ▁within ▁the ▁galax y , ▁suggesting ▁its ▁star ▁formation ▁started ▁at ▁least ▁one ▁billion ▁years ▁ago ▁and ▁possibly ▁as ▁much ▁as ▁ten ▁billion ▁years ▁ago . ▁The ▁galax y , ▁therefore , ▁may ▁have ▁formed ▁at ▁the ▁same ▁time ▁as ▁most ▁other ▁galaxies . ▁ ▁Cont ents ▁ ▁Spect ro scop ic ▁observations ▁with ▁ground - based ▁teles cop es ▁have ▁shown ▁that ▁I ▁Z wick y ▁ 1 8 ▁is ▁almost ▁exclus ively ▁composed ▁of ▁hydro gen ▁and