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SESK: Stuff Everyone Should Know · sesk.info/astro-sun-core-temperature

About how hot is the Sun's core, its hottest part?

About 15 million K, hot enough for hydrogen fusion.

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  1. About 15 million K ✔
  2. About 5800 K
  3. About 1 million K

Why: The core is the Sun's hottest region, at roughly 15 million kelvins. 5800 K is the visible surface, and about a million degrees is the corona.

Huh, didn't know that: The core spans only about 20% of the size of the solar interior, yet it makes all of the Sun's energy.

The dad joke
Why didn't the Sun go to college? Because it already had a million degrees.
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References

Answer: About 15 million K. The core is the Sun's hottest region, at roughly 15 million kelvins. 5800 K is the visible surface, and about a million degrees is the corona.

  1. Astronomy 2e, 15.1 The Structure and Composition of the Sun openstax.org/books/astronomy-2e/pages/15-1-the-structure-and-composition-of-the-sun
    is thought to have a temperature of approximately 15 million K, making it the hottest part of the Sun.
    Checked 2026-10-10.

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