1.   But the helium nucleus winds up with a smaller mass than the sum of those four hydrogen nuclei that fused together.

2.   This multi-step process, which merges the nuclei of hydrogen atoms to form helium nuclei and energy, produces neutrinos.

3.   This process, which merges the nuclei of hydrogen atoms to form helium nuclei and energy, produces neutrinos.

4.   This would presumably decay by emitting a helium nucleus containing two protons.

5.   This yields helium nuclei and tremendous amounts of energy.

6.   But scientists knew it was there because they detected a helium nucleus it emitted as it decayed.

7.   The element is so unstable that it existed only four-thousands of a second before expelling a helium nucleus of two protons and then decaying further.