Fifty light years — that’s about 300,000,000,000,000 (300 quadrillion) miles — away from Earth is Lucy, a former star whose proverbial bulb has burned out. And Lucy’s core has turned into a diamond. In this case, the diamond is huge — the largest in the galaxy. At 10 billion trillion trillion carats — 1 followed by 34 zeroes! — it’s, well, huge beyond imagination. The largest terrestrial diamond, the Golden Jubilee Diamond, is about 500 carats — a 5, followed by two lonely zeroes. How’d this happen? When a star consumes all of its fuel, it burns out, leaving behind a white dwarf — a hot, crystallizing core. For years, scientists have believed that the core, made mostly of carbon, turns into a diamond, but we have had no evidence supporting that thesis. That all changed in 2004, when astronomers were able to use gong-like pulsations emanating from Lucy to determine that its core was a really big diamond and developed the model pictured above.