Why are red stars red, despite being hotter than a blue flame?

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At 1500 C, iron glows “[dazzling white](https://en.wikipedia.org/wiki/Red_heat)”.
At roughly 2000 C, [propane](https://en.wikipedia.org/wiki/Gas_burner) burns [blue](https://en.wikipedia.org/wiki/Gas_burner#/media/File:Propane-burner.jpg).
At 3551 C, [Mu Cephei](https://en.wikipedia.org/wiki/Mu_Cephei) earned the name “Herschel’s Garnet Star”, and this is not a reference to uvarovite.

Why?

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Anonymous 0 Comments

Flames colors are far more dependent upon their composition than their temperature

There’s no green hot but if you add copper sulfate to a fire its gonna be very green

The color you seem from flames at non-astronomical temperature (<3000 C) isn’t determined by blackbody radiation but instead by the electrons of the exhaust hopping between fixed levels. As you add more energy, the CO2 in the smoke hops between higher energy levels causing it to give off higher frequency (bluer) photons

Stars on the other hand have a photosphere(the part that actually emits light) that is at crazy high temperatures which cause it to emit enough blackbody radiation in the visible spectrum to actually be visible. As you crank the temperature of stars up it again shifts the main spike towards bluer wavelengths so you get red, yellow, white, then blue stars.

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