Primordial Proxies Galaxy ScoreCard Milky Way O Abundance (% solar) ~100% Star-Formation Rate (solar masses/year) 2 Stellar & Gas Masses (solar masses) 1011 1010 109 Stars 108 p STELLAR NURSERY Massive stars make oxygen, littering their natal neighborhoods and stars born there. This false-color Hubble image of the Carina Nebula shows oxygen in blue, hydrogen and nitrogen in green, and sulfur in red. Oxygen glows primarily where young stars have carved out the clouds. 26 A PR I L 2 018 * SK Y & TELESCOPE CA RIN A : N ASA / ESA / M. LIVIO / HUBBLE 20TH A NNIVERSA RY TE A M (STSCI); BLUE BACKG ROUND: H A R D IK PE TH A NI / G E T T Y IM AG ES 107 10 6 105 Gas 104 103 102 Gas mass is based on neutral hydrogen content. Astronomers don't have a speciļ¬c estimate for J0811+4730's gas mass, so only its estimated mass in stars is shown. Mass scale is logarithmic. 101 10 0