You might think the coldest place in the universe would just be a random patch of empty deep space. But empty space isn’t quite empty - it’s filled with the faint background “glow” left over from the Big Bang, which keeps it at about 2.7 Kelvin (-270.45°C). That’s the natural temperature floor of the universe.
Except in one place. The Boomerang Nebula, about 5,000 light-years from Earth, is colder than that. Temperatures inside it have been measured at about 1 Kelvin - only one degree above absolute zero. It’s the coldest known natural place in the entire universe.
The reason is a dying star in the middle of the nebula. The star is ejecting gas outward at incredible speed - about 600,000 km/h. As that gas expands rapidly into the surrounding space, it cools dramatically (similar to how a can of compressed air feels cold when you spray it). The expansion is so fast and so steady that the Boomerang Nebula has been getting colder than even the background heat of the universe itself.
