carbon cycle (CN cycle, Bethe-Weizsacker D cycle) - carbon cycle (CN-cycle, Bethe cycle - Veǔc zekker) (opened in 1938-1939). Series of nuclear re stocks in which carbon is a catalyst for the process of converting hydrogen into helium: C(p, y) (P, )O(+)N(p, y)O(+v) N (p, α) "C. To begin with The carbon cycle requires the presence of C and N nuclei and high temperatures (15-20 million K). It depends much more on temperature (E with T15) than the proton-proton cycle (E with T4). Energy is released in the carbon cycle 26 .7 MeV, from which an average of 1.7 MeV is carried away by neutrinos. CNO bi-cycle-double CNO-cycle. Similar to the CN-cycle, but in addition, it also contains the following sequential steps: EN (p. y)O (p. v) "P (Btv) "O (p. a) "N. One such reaction occurs in about 2000 CN cycles. For main-sequence stars with a mass of several Mo, the combustion of hydrogen at double CNO-cycle is the main source of energy (gives about 2% of the energy of the Sun)