Episode 2: What the Universe Is Made Of

After the Big Bang, the universe was composed of just hydrogen, helium, and tiny amounts of lithium. With time, heavier elements were forged in the many generations of stars. After about 8 billion years, the Sun was born, from gas that contained 1.4% of heavier elements. Today, this amount has increased to 2%. The Astronomer’s Periodic Table depicts the three most important constituents of the universe: X (= hydrogen), Y (= helium), and Z (= metals). (In the astronomical sense, “metals” refers to all the elements except hydrogen and helium.) 

Associated Book Chapters from Searching for the Oldest Stars: Ancient Relics from the Early Universe

  • Chapter 1: What Is Stellar Archaeology?
  • Chapter 2: Two Centuries of Pursuing Stars
  • Chapter 3: Stars, Stars, More Stars

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