The planets are heated by the radiant energy of the Sun, which gets weaker with the square of the distance. You know how rapidly the heating effect of a fireplace or an outdoor radiant heater diminishes as you walk away from it; the same effect applies to the Sun. Mercury, the closest planet to the Sun, has a blistering surface temperature that ranges from 280–430 °C on its sunlit side, whereas the surface temperature on Pluto is only about –220 °C, colder than liquid air.
Mercury
Generally speaking, the farther a planet or moon is from the Sun, the cooler its surface.
Source & attribution
Astronomy 2e — Composition and Structure of Planets
OpenStax contributors · OpenStax, Rice University
CC BY 4.0. Text excerpted; whitespace normalised and empty cross-references removed; learning prompts added. No illustrations reproduced.
Source edition: 2024-10-17T15:19:16Z
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