How is nitrogen formed in the universe?

Question

Helium is formed from fusing four hydrogen atoms together. And carbon is formed from fusing helium atoms together. But how is nitrogen formed? Does anyone have the exact process that atoms go through to create nitrogen? I appreciate your help.

Answer 1

Like all the other elements, it's made in stars. Nitrogen is made in the CNO-cycle which takes place to some degree or another in all but the smallest stars. In the CNO-cycle, fusion reactions basically add hydrogen atoms to heavier nuclei to make a heavier element.

Add hydrogen (in other words, a proton) to a Carbon-12 atom, you get a Nitrogen-13 atom. Since odd-numbered isotopes are unstable, that extra proton breaks down into a neutron and a free electron leaving you with Carbon-13. Add another hydrogen atom, and now it's Nitrogen-14, and stable to boot.

In other words, you increase the atomic number by one, and get a stable isotope, by adding two protons in two steps. The same process works for Oxygen, hence the name CNO (Carbon-Nitrogen-Oxygen).

Answer 2

Within the nuclear furnaces of stars. When the star dies all that Nitrogen is released. There was about 4-5 billion years between the Big Bang and the formation of our own solar system, plenty of time for a few quick generations of stars to enrich our nebula cloud with Nitrogen.

Answer 3

Have a look here: http://en.wikipedia.org/wiki/CNO_cycle

The CNO chain reaction of heavier stars can form nitrogen-14 and nitrogen-15

C-13 + H →N-14 + γ

Answer 4

According to the Bethe-Weizsäcker-cycle 14N is formed in stars by fusion of 13C and 1H. Some 14N nuclei escape the stars without colliding with other protons or neutrons. If another proton collides with 14N, 15O is produced, which decays by beta emission to 15N, which is also stable, but rare. If 15N is bombarded by a proton, the reaction produces 12C + 4He. (this last reaction seems a little shaky to me, since 1H + 15N would seem to produce 16O, which is stable)