How massive/hot does a star have to be for fusion to occur

ugalpha

without having to rely on quantum channeling

Astronuc

The core has to get to about 15 million K, although some say about 10 million K.
http://burro.cwru.edu/stu/advanced/stars_birth.html

The sun's mass is about 1048 times the mass of Jupiter, so a mass of hydrogen must have about 0.13 solar mass to start fusion with the pp-chain. This assumes that the cloud from which the star forms is mostly hydrogen.

http://www.duke.edu/~teb/stars/nebula.html

http://abyss.uoregon.edu/~js/ast222/lectures/lec11.html

On the distribution of protostar masses by Philip C. Myers - http://arxiv.org/abs/0910.3120 - or -
http://arxiv.org/ftp/arxiv/papers/0910/0910.3120.pdf

See also - http://iopscience.iop.org/0004-637X/...5147.text.html

Drakkith

Are you referring to Quantum Tunneling? I've never heard of Quantum Channeling.

goldsax

can fusion at 0.13 solar masses occur without quantum tunneling?

infact can nuclear reactions occur without tunneling or can sufficent kinetic energy convey enough energy to get nuclei into actual contact?

Drakkith

I don't believe so. Even at 1 solar mass quantum tunneling is responsible for allowing the proton-proton chain to start by allowing two protons to tunnel close enough to each other for fusion to occur.

Yes, however tunneling will always increase the reaction rate by allowing nuclei that wouldn't normally have enough energy to overcome the columb barrier tunnel through. Even at temperatures high enough for fusion to occur without tunneling, the temperature is only an average. Some particles will be higher and some will be lower. Tunneling allows some of those that are lower to fuse.

qraal

Why even ask? Seems like a pointless question.

qraal

I forgot to add that the potential barrier in p-p fusion is the equivalent of ~10 billion K. That's far too high to occur in any star without tunnelling. And is also why p-p fusion is so very, very slow. Fortunately for all life on Earth.