In their 1994 song “Why does the sun shine?” the rock band They Might be Giants sings, “Hydrogen is built into helium at a temperature of millions of degrees.”
What the band left out was deuterium, the stepping stone stars use to get from hydrogen to helium. Most physicists believe that deuterium as we know it is essential to stars’ ability to shine, and thus to the existence of life itself. But a pair of recent papers throw that long-held assumption into question.