<p>The warmest part of JWST is still hotter (41 <span class="math-container">$^\circ$</span>C) than me.
What I don't understand is where it became so hot (it's been well over 50 <span class="math-container">$^\circ$</span>C for a long time), and why the hottest point doesn't cool faster.</p>
<p>Is there a napkin friendly calculation to understand how much heat escapes JWST?</p>

CC BY-SA 4.0
2022-02-12T00:44:25.553Z
It’s been sitting in direct sunlight for several weeks…
Peter Erwin
CC BY-SA 4.0
2022-02-12T01:23:17.120Z
@PeterErwin And never in the shade.
David Hammen
CC BY-SA 4.0
2022-02-12T01:23:21.647Z
The effective equilibrium temperature of a flat plane that is always face-on to the Sun with the same albedo as the Earth and that orbits about 1 AU from the Sun is $\sqrt 2$ times the absolute effective equilibrium temperature of the Earth. That makes that flat plane have an effective equilibrium temperature of about 360 kelvins, or about 87° C.
David Hammen
CC BY-SA 4.0
2022-02-12T09:00:35.437Z
I think that already constitutes 60% of an answer, if not a full one @DavidHammen
planetmaker
<james-webb-space-telescope>
James Webb hot temperature
Captain Giraffe
# James Webb hot temperature

(Asked by: username_0 on 2022-02-11)

The warmest part of JWST is still hotter (41 $^\circ$C) than me.
What I don't understand is where it became so hot (it's been well over 50 $^\circ$C for a long time), and why the hottest point doesn't cool faster.

Is there a napkin friendly calculation to understand how much heat escapes JWST?

**Tags:** james-webb-space-telescope

> **Comments:**
> **username_1**: It’s been sitting in direct sunlight for several weeks…  
> **username_2**: @PeterErwin And never in the shade.  
> **username_2**: The effective equilibrium temperature of a flat plane that is always face-on to the Sun with the same albedo as the Earth and that orbits about 1 AU from the Sun is $\sqrt 2$ times the absolute effective equilibrium temperature of the Earth. That makes that flat plane have an effective equilibrium temperature of about 360 kelvins, or about 87° C.  
> **username_3**: I think that already constitutes 60% of an answer, if not a full one @DavidHammen  

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## 0 answers

