Is the sun hotter on the inside, or the outside of the sun?

The Sun is much hotter on the inside. At the surface it is only about ten thousand Fahrenheit degrees (about 6000 Kelvins), while in the center it is almost thirty million Fahrenheit degrees (about 15,000,000 Kelvins). In fact for any star to be stable it must become brighter and brighter as you go toward its center, and the only way to achieve that is for it to become hotter. So all normal stars are much hotter on the inside than on the outside, in extreme cases reaching central temperatures of billions of degrees during the last stages of their 'life'.

Although possibly going into more detail than you want, you might find it useful to read Heat Flow in the Solar Interior (at ). There is also a similar but somewhat more thorough discussion of the topic on another page, Review of Heat Flow Inside Stars (at ).


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Courtney Seligman


I can answer almost any question about astronomy and related sciences, such as physics and geology. I will not answer questions about astrology and similar pseudo-scientific rubbish.


I have been a professor of astronomy for over 40 years, and am working on an online text/encyclopedia of astronomy, and an online catalog of NGC/IC objects.

Astronomical Journal, Publications of the Astronomical Society of the Pacific (too long ago to be really relevant, but you could search for Courtney Seligman on Google Scholar)

I received a BA in astronomy and physics and a MA in astronomy, both from UCLA. I was working on my doctoral dissertation when I started teaching, and discovered that I preferred teaching to research.

Awards and Honors
(too long ago to be relevant, but Phi Beta Kappa and Sigma Xi still keep trying to get me to become a paying member)

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