Arecibo Observatory image courtesy of H. Schweiker/WIYN and NOAO/AURA/NSF

Iran reached an agreement with the P5+1 countries—the five permanent members of the United Nations Security Council plus Germany—to limit Iran’s nuclear program. The deal requires Iran to reduce its stockpile of low-enriched uranium by 98% for 15 years. Iran also agreed to cut the number of centrifuges it currently uses to enrich uranium roughly in half and to enrich uranium to no more than 3.7% U-235 (the isotope that powers both nuclear reactors and nuclear weapons). Nuclear …