A lot of the periodic table is a result of neutron stars colliding

LIVING THINGS are star stuff. Other than hydrogen, which comes from the Big Bang, which marked the birth of the universe, the familiar elements of which flesh is composed—carbon, oxygen, nitrogen and so on—were created by the energy-releasing process of nuclear fusion that powers stars. But fusion has its limits. The balance of forces inside an atomic nucleus means that creating an element heavier than iron (number 26 on the periodic table) consumes energy, rather than releasing it. Further up the table, beyond lead (number 82), nuclei tend to fall apart spontaneously. In other words, they become radioactive.

To synthesise elements heavier than iron—and particularly those heavier than lead—therefore requires a lot of work. Some of this work happens in stellar explosions called supernovae. Calculations suggest, however, that even supernovae would be hard put to explain the abundance of the heaviest elements, including metals such as gold and platinum as well as radioactive ones like uranium. One hypothesis is that these elements are the products of collisions between ultradense objects called neutron stars. And, as Brian Metzger of Columbia University told the AAAS, that hypothesis has now been confirmed by data.