How cold is outer space

Photos from open sources

Probably few people thought about what would happen if you are in space without protection? In addition to the obvious lack of oxygen and slow suffocation, a person will also be exposed to extreme temperatures that can not only kill, but also make the last seconds in the universe very uncomfortable.

There is an assumption that it is extremely cold in space, and that is mostly correct – with some caveats. It depends very much on where you are in outer space. There is an option to both freeze and burn, and there are places where even a spaceship will melt.

So how cold is outer space near Earth? The International Space Station (ISS) is only 400 kilometers above Earth, but without the protection of the atmosphere it experiences extreme temperatures not seen on Earth.

At the lowest temperatures, thermometers will register around -157°C, a temperature at which even pure propyl alcohol freezes. This happens when the ISS passes behind the Earth. When the station is back in the sun, the temperature jumps to 121°C. Similar extremes are observed on the Moon between its day and night sides.

The temperature in interplanetary space depends on how close you are to the Sun. And you don’t have to get too close to reach incredibly high temperatures.

The corona, the solar atmosphere, stretches over millions of kilometers and at its hottest has a temperature of millions of degrees. Passing through the outer layers of the corona, NASA’s Parker Solar Probe does not have a camera pointed at the Sun, because by getting so close the sunlight would be hot enough to melt the interior of the spacecraft.

Temperature fluctuations are observed near all large space objects. Stars, black holes, planets and more affect the temperature in the environment. But in fact we can measure the temperature of space as a whole.

This dimension comes from the cosmic microwave background, the first light that could move freely through the universe.

In the early universe, everything was so hot that this light was constantly removing electrons from atoms, being absorbed and then re-emitted in the process. Due to the expansion of the universe, it began to cool until this light became free.

Since then, the universe has expanded and cooled. Right now the temperature is -270.4° C. Just a few degrees above absolute zero, the lowest temperature.

How hot a substance is actually depends on how energetic its particles are: the more energy, the more heat. At absolute zero, particles have zero energy and are stationary.

Certainly there are hotter places in the universe, even in intergalactic space, thanks to jets of material accelerated by supermassive black holes, as well as gas drawn in by gravity.

Surprisingly, there are also colder places than the CMB. The Boomerang Nebula is one of them, and scientists only recently figured out how it gets a little colder than the rest of the universe.

Space suits are not designed to keep you warm. They are designed to maintain a comfortable temperature for astronauts, regardless of the outside temperature. And that, as already mentioned, can fluctuate greatly around the Earth.


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