Astrophysics (index)

CNO Cycle

(fusion reaction chain turning hydrogen and nitrogen into helium and nitrogen)

A CNO Cycle is a fusion reaction in stars turning Hydrogen (H) into Helium (He) if Nitrogen (N) is present along with sufficient Temperature. It is one of two reactions turning hydrogen into helium, the other being the Proton-Proton Chain, which is independent of nitrogen.

Larger, hotter stars use this more and it is the primary reaction in stars of more than 1.3 solar masses.

The CNO cycle was proposed by Carl von Weizsacker and Hans Bethe in 1938 and 1939.

There are 7 CNO cycles, CNO-I, CNO-II, CNO-III, and CNO-IV, the other being hot cycles, HCNO-I, HCNO-II, and HCNO-III.

Example (6 steps of CNO-I):

12    1     13
  C +  H →    N + Y       + 1.9  MeV
 6    1      7

13          13     +
  N      →    C + e  + v  + 1.20 MeV (9.965 minute half-life)
 7           6          e

13    1     14
  C +  H →    N + Y       + 7.54 MeV
 6    1      7

14    1     15
  N +  H →    O + Y       + 7.35 MeV
 7    1      8

15          15     +
  O      →    N + e + v   + 1.73 MeV (122.24 second half-life)
 8           7         e

15    1     12    4
  N +  H →    O +  H      + 4.96 MeV
 7    1      6    2

(fusion,nuclear,reaction,nucleosynthesis)
http://en.wikipedia.org/wiki/CNO_cycle

Referenced by:
Carbon (C)
Main Sequence Star
Nova
Nucleosynthesis
Oxygen (O)
Proton-Proton Chain
Stellar Core
Stellar Structure

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