There’s a fresh twist in the mystery of the “little red dots.” Astronomers say they’ve found a new specimen, which they’re calling an “X-ray dot,” that suggests these crimson specks are a type of never-before-seen — and improbably extreme — stage of supermassive black hole evolution. The breakthrough, which they report in a new study published in The Astrophysical Journal Letters, came from data taken by NASA’s Chandra X-ray Observatory. By com…