Doomstar — Edmond Hamilton

The sun shone brightly on this fateful morning, bringing to its planets warmth and life-giving rays. The brightness increased sharply as the morning grew older. The glare was blinding; the radiation not life-giving, but deadly. By mid-afternoon the brilliant, intense sun shone on barren space. It had blasted each of its four planets out of existence.

Someone had found a way to poison a star

And someone had to be found who could prevent the takeover or destruction of the entire universe. Who? Johnny Kettrick, as improbable a hero there never was. Johnny Kettrick who was banned from the Cluster World for his not-too-honest dealings was sent back there with his three equally unholy partners to search out the Doomstar...to find the Doomstar before it burned out another world.