Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. HD 122563 is an extremely metal poor red giant star, and the brightest metal poor star in the sky. Its low heavy element content was first recognized by spectroscopic analysis in 1963. For more than twenty years it was the most metal-poor star known, being more metal-poor than any known globular cluster, and it is the most accessible example of an extreme Population II or Halo star. As the most extreme metal-poor star known, HD 122563's composition was crucial in constraining theories for galactic chemical evolution; in particular, its composition peculiarities provided signposts for understanding the accumulation of heavy elements by stellar nucleosynthesis in the Galaxy.