[thisisbrians]

you're probably getting downvoted because there isn't really a temperature 4 million miles away from the Sun (it's mostly just empty space being bombarded by radiation)

2,500º F is merely the temperature the probe is expected to reach at that distance. if it were to stay at that distance indefinitely, it would grow much, much hotter as it absorbed more energy from the sun.

[tomnicholas1]

No not necessarily - it will keep growing hotter until the black body radiation emitted by the probe matches the power of the radiation hitting the probe. Then it will stay at constant temperature.

It's a standard undergraduate problem to work out what this equilibrium temperature is for a flat plate at a distance from the sun equal to the Earth's orbital radius.

Interestingly the result is only a few 10's of degrees less than the average temperature of the real Earth - the difference is due to the Greenhouse Effect.

For the probe one could easily do the maths but I could believe that at 4 million miles that equilibrium temperature is 2,500F.

[thisisbrians]

i definitely can't do the math myself, but excellent retort. thank you for the nuance

[feoren]

Temperature is so wibbly-wobbly. The probe will reach an equilibrium energy-in vs. energy-out temperature depending on its distance from the sun, its surface area facing the sun, and the materials being lit, vs. its surface area facing away, the thermal radiation rate of various materials, and other factors. You could give an aerospace engineer almost any temperature between the CMB and the surface of the sun and they could probably design a (at least theoretical) probe that would reach that temperature eventually* at almost any distance. My guess is that 2500 ºF probably is the equilibrium temperature of the probe at that distance.

* With "eventually" being "assuming a stable state for infinite years" which is of course not how astrophysics actually works.

[lazide]

Eh, not quite yeah?

You’re talking about heat (think ‘amperage’), where temperature is more like voltage.

You can’t get above a specific temperature merely by transferring more heat, or losing less heat, etc.

Upper bounds of temperature is still going to be limited by the temperature/frequency of the input energy, barring energy loss which can reduce it.

The solar atmosphere layers have specific maximum temperatures that limit the maximum temperature of objects exposed to them or the radiation from them.