title: Astronomy: an elementary puzzle.
authors.forename: Eddie
authors.initials: E
authors.lastname: Baron
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D019418:Evolution, Chemical; D005118:Extraterrestrial Environment / Q000737:chemistry*; D005740:Gases / Q000032:analysis; D006859:Hydrogen / Q000032:analysis*
chemical_list: D005740:Gases; D006859:Hydrogen