Old Star, New Trick: Astronomers Have Detected Arsenic and Selenium in Ancient Star for First Time

The Big Bang produced lots of hydrogen and helium and a smidgen of lithium. All heavier elements found on the periodic table have been produced by stars over the last 13.7 billion years. Astronomers analyze starlight to determine the chemical makeup of stars, the origin of the elements, the ages of stars, and the evolution of galaxies and the universe. Now for the first time, astronomers have detected the presence of arsenic and selenium, neighboring elements near the middle of the periodic table, in an ancient star in the faint stellar halo that surrounds the Milky Way. Arsenic and selenium are elements at the transition from light to heavy element production, and have not been found in old stars until now.