What is the CNO cycle
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What is the CNO cycle

[From: ] [author: ] [Date: 13-03-03] [Hit: ]
E) the period of a low-mass stars life when it can no longer fuse carbon, nitrogen,Alright so Im quite confused about this question, I know its a fusion of 4 hydrogen nuclei into an helium nucleus but from this Im not really sure which it is? I was thinking D, but Im not entirely sure.......
A) the process by which carbon is fused into nitrogen and oxygen
B) the process by which helium is fused into carbon, nitrogen, and oxygen
C) the period of a massive star's life when carbon, nitrogen, and oxygen are fusing in different shells outside the core
D) a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts
E) the period of a low-mass star's life when it can no longer fuse carbon, nitrogen, and oxygen in its core

Alright so I'm quite confused about this question, I know it's a fusion of 4 hydrogen nuclei into an helium nucleus but from this I'm not really sure which it is? I was thinking D, but I'm not entirely sure. Thanks.

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It is is D)

D) a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts


Your confusion is understandable. The CNO cycle is NOT the predominant cycle in low mass stars like the Sun. The Sun's predominant way of fusing hydrogen into helium is proton proton chain reaction The Sun does fuse hydrogen into helium with the CNO cycle in the core, where the temperatures and pressures are high enough, but that is not how the Sun gets most of its energy. In HIGH mass hot stars like Sirius, Vega and Deneb the CNO cycle is the predominant cycle.

"...Also called the carbon-nitrogen-oxygen cycle, a cycle of six consecutive nuclear reactions resulting in the formation of a helium nucleus from four protons. The carbon nuclei with which the cycle starts are effectively reformed at the end and therefore act as a catalyst. This is believed to be the predominant energy-producing mechanism in stars with a core temperature exceeding about 18 million °C. In lower-mass stars with a lower core temperature, the proton-proton chain predominates..."

http://www.daviddarling.info/encyclopedi…


http://www.daviddarling.info/encyclopedi…

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Yes, it is D but it only occurs in stars 1.3 times our Sun's mass, the carbon, nitrogen and oxygen are the same atom just undergoing transformations from one to the other.

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read the link and learn something
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