The chemical composition of the interstellar medium.
D001128:Argon / Q000032:analysis; D055580:Astronomical Phenomena; D001256:Astronomy; D002244:Carbon / Q000032:analysis; D055598:Chemical Phenomena; D002621:Chemistry; D002713:Chlorine / Q000032:analysis; D003359:Cosmic Radiation; D004602:Elements / Q000032:analysis*; D006371:Helium / Q000032:analysis; D006859:Hydrogen / Q000032:analysis; D007259:Infrared Rays; D007477:Ions / Q000032:analysis; D008433:Mathematics; D009405:Neptunium / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010100:Oxygen / Q000032:analysis; D011846:Radio Waves; D013057:Spectrum Analysis; D013455:Sulfur / Q000032:analysis; D014466:Ultraviolet Rays
D004602:Elements; D007477:Ions; D006371:Helium; D002713:Chlorine; D009405:Neptunium; D001128:Argon; D013455:Sulfur; D002244:Carbon; D006859:Hydrogen; D009584:Nitrogen; D010100:Oxygen