The visible Universe is full of temperature extremes.
It’s true: the past was hotter and the future will be colder.
But even today, incredibly hot and cold extremes are ubiquitous.
The hottest environments exist around natural particle accelerators: supermassive black holes.
When active, their accelerated particles maximally achieve ~1020 eV energies, implying ~1024 K temperatures.
Neutron star interiors come next, where quark-gluon plasmas peak at T ~ 1012 K.
The centers of massive stars reach 108-109 K, necessary to fuse heavy elements.
The hottest gas/plasma clouds reach several million degrees.
Neutron star surfaces and white dwarf interiors are slightly cooler: from 105-106 K.
Next, giant planet interiors and white dwarf surfaces measure 8,000-50,000 K.
Stellar surfaces are relatively cooler: 2700 K and up.
Brown dwarfs and hot planets achieve ~500-2000+ K.
Planetary bodies range from thousands down to tens of degrees, determined by their orbital distances.
In interstellar space, temperatures are merely 10-30 K.
Deep, intergalactic space achieves 2.725 K: heated only by the CMB.
But rapidly expanding gases achieve the coldest natural temperatures.
Preplanetary nebulae, like the Boomerang Nebula, achieve temperatures from 0.5-1.0 K.
Today, only laboratory experiments achieve colder conditions.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.