Dark Matter Search Discovers A Spectacular Bonus: The Longest-Lived Unstable Element Ever

The XENON collaboration has just publicly announced the discovery that xenon-124, an isotope of the element Xenon, is fundamentally unstable. Its half-life is a whopping 1.8 × 10²² years: more than one trillion times the present age of the Universe.
 
More details on the discovery can be found here, and the Nature paper can be found here.