How cold is it in space what processes affect the temperature of the universe

(ORDO NEWS) — How cold is outer space, does its temperature drop to absolute zero, and what happens if you get there without a spacesuit?

While sci-fi movies lead us to believe that space is incredibly cold, even icy, space itself is not entirely cold. In fact, he has no temperature at all.

What is temperature and is it in space?

Temperature consists of the speed at which particles are moving and the energy emitted by them as they move. Thus, in a truly empty space, there would be no particles and radiation, and therefore no temperature.

Of course, space is full of particles that radiate energy as they move, which means they produce heat and temperature. How cold is it in space, is there an area that is truly empty, and is there a place where the temperature drops to absolute zero?

Hot regions of space are located directly around the stars, where there are all conditions for launching nuclear fusion. There, objects really heat up when the star’s radiation reaches a point in space with a large number and density of particles that can be affected by temperature.

That is why the Earth is much warmer than the region between our planet and its star. Heat comes from particles in our atmosphere that vibrate with solar energy and then collide with each other, distributing that energy.

How cold is it in space what processes affect the temperature of the universe 2
The cluster of galaxies RXJ1347 is one of the hottest places in the Universe

However, proximity to a star does not always guarantee warmth. For example, Mercury is the closest planet to our Sun. It is incredibly hot during the day and terribly cold at night. Its temperature drops to -178 degrees Celsius.

Temperatures on Uranus drop to -224⁰C, making it even colder than Neptune, the furthest from the Sun. By the way, Neptune is still terribly cold – its temperature reaches -214⁰C.

This is the result of a collision with an Earth-sized object early in the formation of the planet, which is why Uranus, for example, orbits the Sun at an extreme tilt, which prevents it from retaining internal heat.

The farther from the star, the colder

Away from the stars, the particles are so scattered (their density is less) that heat transfer through anything other than radiation is impossible, which means that the temperature drops sharply. This region is called interstellar space.

Heating mechanisms of the interstellar medium

  • Heating by low-energy cosmic rays
  • Photoelectric Dust Heating
  • Photoionization
  • X-ray heating
  • Chemical heating
  • Heating of dust particles

Cooling mechanisms of the interstellar medium

  • Cooling by radiation of fine structure lines
  • Cooling by radiation of allowed lines

The coldest and densest clouds of molecular gas in the interstellar medium can be as cold as -263⁰C, while the less dense clouds can be as cold as -173⁰C.

The universe is so wide and filled with so many objects that some are incredibly hot while others are incredibly cold. Therefore, space simply cannot have a uniform temperature.

At the same time, there is something that permeates our entire universe with a temperature of one hundred thousandth. In fact, the difference is so small that the difference between a hot spot and a cold spot is only 0.000018 K.

We are talking about the cosmic microwave background (CMB), better known as the cosmic microwave background. It has a uniform temperature of 2.7 K (-270⁰C). Since 0 K is absolute zero, this temperature is only 2.725 degrees above absolute zero.

The CMB is a remnant of what happened only 400,000 years after the phenomenon known as the Big Bang. Although for a correct understanding it should be called the Great Scattering.

This is the moment when the universe ceased to be opaque after electrons combined with protons to form hydrogen atoms, which stopped the endless scattering of light by electrons and allowed photons to travel freely.

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Map of the cosmic microwave background recorded by the WMAP telescope for 9 years

So this relic fossil “frozen” into the universe is the last point where matter and photons were aligned in terms of temperature.

The photons that make up the CMB were not always so cold, they took about 13.8 billion years to get to us. The expansion of the universe has redshifted these photons to lower energy levels.

The CMB originated when the universe was much denser and hotter than it is now. Its initial temperature is estimated to be around 2726⁰C. As the universe continues to expand, this means that space is now colder than ever and temperatures continue to drop.

What happens if you go into space without a spacesuit?

If an astronaut were left to drift alone in space, then the influence of the near vacuum of space could not freeze the astronaut, as is often portrayed in science fiction.

There are three ways to transfer heat:

  • Thermal conductivity – occurs through touch
  • Convection – occurs when fluids transfer heat
  • And radiation is due to radiation

Conduction and convection cannot occur in empty space due to the absence of matter, and heat transfer occurs slowly by radiative processes. This means that heat does not transfer quickly in space.

Since freezing requires heat transfer, an astronaut exposed to radiation having lost heat only through radiative processes will die from decompression due to the absence of an atmosphere much faster than freezing to death.


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