1.   Eventually, however, the hydrogen in the core runs out and so nuclear reactions involving heavier elements take over.

2.   At the end of its life, the sun is expected to fuse helium into heavier elements and expand, growing so large that it will swallow the Earth.

3.   All manmade elements heavier than uranium decay radioactively, and generally speaking, the heavier the element, the faster the decay.

4.   Heavier elements formed later inside stars, where nuclear reactions jammed protons and neutrons together to make new atomic nuclei.

5.   In the sun, energy is produced when hydrogen nuclei fuse to produce helium, a heavier element.

6.   It also raised its estimate for the Nevada Test Site, near Las Vegas, where the heavier elements are the result of nuclear test detonations.

7.   It also consumes its helium, producing heavier elements like carbon and oxygen.

8.   Larger stars build even heavier elements.

9.   The age is then confirmed by measuring levels of strontium, which slowly accumulates from the decay of heavier elements.

10.   The radioactive elements at issue are elements heavier than uranium, produced in reactors by bombarding uranium with neutrons to make plutonium for weapons.