Physicists have created the heaviest isotope yet of magnesium, but in their experiments an unexpected isotope of aluminum also showed up. The findings could help astrophysicists understand occasional X-ray emissions from neutron stars that are growing in mass. The 7-day-long experiment took place at the National Superconducting Cyclotron Laboratory (NSCL), an atom smasher at Michigan State University in East Lansing. Hoping to test the limits of how many extra neutrons will bind to an atomic nucleus, researchers were trying to create magnesium-40, a heavyweight element with 18 more neutrons than the most common isotope, magnesium-22. Standard theory says that magnesium-40...