Does Space Have a Temperature?

Measuring the temperature in space is much more complicated than simply using a thermometer. This is because temperature can only be a ‘meaningful figure’ when heat can be properly transferred from one body to another.

Measuring the temperature in space is tricky because the density of particles is very low, despite the fact that their temperatures can be quite high. This makes the process of heat exchange very unlikely.

So, scientists can estimate the number of degrees using Kelvin but, due to the fact that these particles very rarely collide with each other, the heat is rarely transferred.

To get around this, measuring temperature in space is more about how molecules move and are concentrated. This determines how often they bump into each other to gain or lose energy.

Calculating the temperature in space can be broken down into two parts. The first is ‘outer space’. This is generally considered as the part of the Universe that is practically empty and begins at about 62 miles above sea level, from our perspective here on Earth.

The second, is the void between galaxies, star systems and planets. Here, the temperature is thought to be 2.72 Kelvin or -454.71 Fahrenheit. This is just a small amount above absolute zero! Absolute zero is the point at which matter is no longer able to move and is believed to be -459.67 Fahrenheit.

The estimation of 2.72 Kelvin is just an average temperature which is measured using Cosmic Background Radiation. This is the energy left over from the Big Bang.

When you look closer to Earth, the temperature is believed to be more like 35 to 40 Kelvin as a result of the Sun’s rays. While this is still incredibly cold, nowhere in space is as cold as it is in ‘deep space’ where there is no heat from the Sun.

How cold is space?

Space is extremely cold. This is primarily because of the vacuum-like nature of space as well as the lack of atmosphere.

There are very few molecules in space to move around and bump into each other so the heat transfer process cannot happen.

In the empty space between planets and other galaxies, it is thought the temperature is around 2.7 Kelvin or -454.81 Fahrenheit, on average. But, it’s important to remember that the makeup of space is extremely varied and some parts are much colder than others.

At 2.7 Kelvin, this is just a small amount above absolute zero, the point at which the movement of matter ceases. So, at 2.7 Kelvin nothing strange happens and everything we know about physics still makes sense.

Beyond this would be going into quantum territory and to do this we would have to go a lot colder.

As explained above, measuring the temperature in space is often divided into two sections: outer space and the void between galaxies, planets and stars etc.

Outer space is generally considered as the part of the Universe that is practically empty and begins at about 62 miles above sea level, from our perspective here on Earth.

The estimation of 2.72 Kelvin is just an average temperature which is measured using Cosmic Background Radiation. This is the energy left over from the Big Bang.

When you look closer to Earth, the temperature is believed to be more like 35 to 40 Kelvin as a result of the Sun’s rays. While this is still incredibly cold, nowhere in space is as cold as it is in ‘deep space’ where there is no heat from the Sun.

The planets in our solar system are very cold. Depending on the distance a planet is from our Sun, the colder they generally tend to be. Although, Venus is the exception to the rule.

Despite its distance from the Sun being further than that of Mercury, its dense atmosphere makes it the hottest planet in our solar system. The dense atmosphere acts as a greenhouse heating the surface to about 880 degrees Fahrenheit!

Below is a quick breakdown of the temperatures of the planets in our solar system in Fahrenheit and Celsius for comparison:

  • Mercury: 800°F (430°C) during the day and -290°F (-180°C) during the night
  • Venus: 880°F (471°C)
  • Earth: 61°F (16°C)
  • Mars: minus 20°F (-28°C)
  • Jupiter: minus 162°F (-108°C)
  • Saturn: minus 218°F (-138°C)
  • Uranus: minus 320°F (-195°C)
  • Neptune: minus 331°F (-201°C)
  • Pluto: minus 388°F (-233°C)

Despite being the furthest planet from the Sun, Neptune doesn’t have the lowest average temperature.

Rather, Uranus is considered the coldest planet in the solar system with an average temperature of -320 degrees Fahrenheit.

The planet’s distance from the Sun is the main contributor to its freezing temperatures. Being 19 times further away from the Sun than Earth.

What is the coldest thing in the universe?

To our knowledge, the coldest thing in the Universe is currently the Boomerang nebula. This spot can be found 5,000 light-years away from Earth. It is estimated to be just 1 Kelvin or -457.87 degrees Fahrenheit!

The Boomerang nebula is situated in a large constellation in the southern sky within the Milky Way called Centaurus, a large constellation in the southern sky. It is a cloud of gas that is being expelled from a dying star.

As the coldest measured object in the Universe, it is also the most enigmatic and exciting. Inside the cloud where gas streams outwards, scientists have discovered that its temperature drops to as low as half a degree above absolute zero!

The coldest spot in our solar system is actually quite close to us. Craters near the South Pole of the Moon have measured at 33 Kelvin or -400.27 degrees Fahrenheit.

These craters are thought to be so cold because they are permanently shadowed. This is even colder than Pluto which is very dark and remote.

The lowest temperature scientifically possible is -459.67 degrees Fahrenheit. It is believed that beyond this, matter will not be able to move.

Gordon Watts
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