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I've heard that if a space shuttle enters the atmosphere from a bad angle its surface will become so hot that it will be hotter than the surface of the Sun.

How can that be? It seems to an uneducated mind that Sun is really really hot, how could something seemingly minor such as a wrong angle of entrance to the earth's atmosphere could end up generating a heat hotter than the Sun?

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    $\begingroup$ IMO, the interesting subquestion here is: Why is the Sun's surface that cold? The current answers do not address that. $\endgroup$ – Řídící Apr 28 '13 at 18:11
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As for the question of whether anything can be hotter than the sun. The Sun is composed of plasma, an energetic phase of matter in which electrons get ripped off of atoms, and electrons and ions coexist in something that might best be described as an ionized gas.

According to this wiki page, the so-called Z machine has achieved temperatures on the order of $10^9\,\mathrm K$ (billions of Kelvin) which is even hotter than the Sun's core which is apparently at around $10^7\,\mathrm K$ according to the physical characteristics listed here.

Thanks to user Gugg who points out that apparently Brookhaven is recognized as having achieved the hottest man-made temperature on the order of $10^{12}\,\mathrm K$. See the link he provides down below.

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    $\begingroup$ How about $4\cdot10^{12}\ \text{K}$? $\endgroup$ – Řídící Apr 28 '13 at 17:56
  • $\begingroup$ @Gugg Cool; I included this in the post. $\endgroup$ – joshphysics Apr 28 '13 at 18:04
  • $\begingroup$ @GlenTheUdderboat ALICE the experiment has 5.5 e12 K humps. $\endgroup$ – Yakk Jul 20 '15 at 18:05
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It depends on many factors such as the reentry velocity of the object, its shape (cone-spherical, etc.), what the planet's atmosphere is made of, whether it enters at some shallow angle and also the altitude where there's density variations in atmosphere, etc.

Googling on this, could return you a lot of results. And, all results matched a certain value. Here's the Wiki article on Thermal Protection which has its first phrase...

The Space Shuttle thermal protection system (TPS) is the barrier that protected the Space Shuttle Orbiter during the searing 1,650 °C (3,000 °F) heat of atmospheric reentry. A secondary goal was to protect from the heat and cold of space while on orbit

It's clear that it's nearly 4 times lower than the temperature of sun (5500 °C) When you hear things which you doubt, you should be skeptical and be sure to google it first...

And of course, a space shuttle entering at a bad angle (as you say) can have temperatures very much higher than $T_{sun}$. Here's a Wiki link (suggested by Gugg)

For example, a spacecraft entering the atmosphere at 7.8 km/s would experience a peak shock layer temperature of 7800 K.

But, it's still lower than the temperature of corona.

Your question's title is somewhat ambiguous. There are infinitely many number of celestial objects that are at a higher temperature than the sun (probably higher than its core).

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  • $\begingroup$ Hmm, just googling on, I wondered if you took the "bad angle" in the question into account. $\endgroup$ – Řídící Apr 28 '13 at 18:06
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    $\begingroup$ "For example, a spacecraft entering the atmosphere at $7.8\ \text{km/s}$ would experience a peak shock layer temperature of $7800\ \text{K}$." (See the link in my previous comment.) I think it would be more interesting to have explained why the Sun's surface is that cool. $\endgroup$ – Řídící Apr 28 '13 at 18:16
  • $\begingroup$ Hi @Gugg: I'll include the Wiki link. But, I think I don't understand correctly what you really expect. The sun's surface is cool (while the corona is considerably hotter) because of its geometry, the luminosity decreases with distance and the flux (power transmitted) to its photosphere and hence the temperature is very much lower than the core ;-) $\endgroup$ – Waffle's Crazy Peanut Apr 28 '13 at 18:32
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    $\begingroup$ And..., this is obvious? :) There's some discussion here, but strangely it seems to suggest (on quick reading) that the surface (not the corona) temperature somehow... isn't. :) It's a "black-body temperature equivalent"? Which would contradict Wikipedia? $\endgroup$ – Řídící Apr 28 '13 at 18:42
  • $\begingroup$ +1 for mentioning the temperature of the sun's surface rather than core. $\endgroup$ – dave Nov 11 '13 at 3:42
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The temperature of our sun is determined primarily by the generation of heat (the fusion process) and the rate of heat loss by various means. When the process reaches equilibrium, a given average temperature is maintained. Any other process that has a higher generation rate or smaller energy loss, or both, would be hotter than our sun.

In the case of the shield, the temperature could be hotter than our sun, but only for a short time. This would not be a fair comparison because we would be using the average sun temperature against the peak temperature generated by the shield.

In the universe, there are other suns that are indeed much hotter than our sun.

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